UC-NRLF 


B   ^   MDO   Mtl 


MERRITT 


iflKflfY 

LIBRARY 

UKHVERSITY  OP 
CALIFORNIA 


Bausch  &  Lomb 

Optical 
Machinery 

Designed  from  our  own  ex- 
perience of  nearly  70  years 
as  quality  lens  grinders — 
with  the  aim  of  providing 
optometrists  and  opticians 
wnth  shop  equipment  equal 
to  that  employed  by  us. 

All  models  have  withstood 
the  practical  test  of  daily  use 
in  our  own  shops. 

The  new  Automatic  Surfac- 
ing Machine,  here  illustrated,  has  been  enthusiasti- 
cally approved  by  all  shopmen  who  have  tried  it,  or 
seen  it  demonstrated.  Featured  by  simplicity,  com- 
pactness and  economy  in  operation,  it  will  surface 
almost  unlimited  range  of  surfaces,  even  deepest 
curved,  without  evidence  of  waves.  Unit  of  several 
machines  easily  controlled  by  one  man  or  woman 
operator. 

Write  for  illustrated  circular  describing  our  Automatic,  Semi- 
Automatic  and  Hand  Surfacing  Machines,  Edging  Machine, 
Little  Gem  Lens  Cutter,  Blocking  Stand  and  other  accessories. 

B«wsGh:£^  Ipmb  Optical  (5. 

NEW  YORK  WASHINGTON  SAN  FRANCISCO 

CHICAGO  BOCHESTEB.    N.   Y.  LONDON 

Leading  American  Makers  of  Ophthalmic  Lenses  and  Instruments, 
Microscopes,  Projection  Lanterns  {Balopticons) ,  Binoculars,  Mag- 
nifiers,^ Readers  and  Other  Optical  Products. 


^TOCi 


Optical  Machinery 

The  best  recommendation  of 
^wco)  Optical  Machinery  is 
the  fact  that  it  is  difficult  to 
find  a  prescription  shop  in  the 
United  States  in  which  it  is 
not  used. 

Catalog  on  request. 

The  Standard  Optical  Co. 

GENEVA,  N.  Y. 


WILLIAM  W,  MERRITT 


OPTOCAL  SHOP  PRACTICE 

By 
WILLIAM  W.  MERRITT 

Instructor  in  Mechanical  Optics,  Northern  Illinois  Colleg : 
of  Ophthalmology  and  Otology. 


n  n  «=> 


A  text  book  for  the  Beginner. 
A  complete  treatise  on  Optical 
Shop  Practice,  with  the  col- 
laboration of  the  greatest  me- 
chanical minds  in  the  trade. 


D  n  ° 


Copyright  1920 

Price  $2.00 


Published  by 

THE  PROFESSIONAL  PRESS,  Inc. 
Chicago 


iPTDML  SHOP  FB^CTBC 

n  D  D 


The  optical  business  has  passed  through  its  embryonic 
stage  and  has  emerged  into  the  world  of  science.  It  has 
attained  a  position  wherein  modern  thought  and  achiev- 
ment  hade  made  it  a  vital  part  of  our  daily  life,  for  the 
exacting  qualifications  of  modern  times  demand  quick- 
ness of  perception,  and  the  faculty  of  perception  depends 
upon  the  eye  to  a  very  great  degree.  Accuracy  is  the 
paramount  factor  in  meeting  these  requirements — scien- 
tific accuracy.  However,  despite  this  condition,  the 
practice  of  optical  work  is  simple  enough,  if  those  who 
follow  it  adhere  to  the  fixed  rule  of  following  demonstrated 
procedures  governed  by  good  judgment.  Very  few  indi- 
viduals are  without  the  power  of  concentration  to  a  greater 
or  less  extent,  and  this  faculty  can  be  cultivated  by 
practice  and  care.  Just  as  the  babe  must  first  learn  to 
stand  alone  before  being  able  to  walk  and  then  to  run, ' 
the  optical  shopman  must  go  at  his  work  by  easy  stages 
and  by  persistence  will  finally  master  his  objective. 

This  volume  has  been  designed  for  the  beginner.  It  is 
writter  in  simplified  form,  avoiding  technical  language 
as  much  as  possible,  and  the  average  boy  or  girl  of  fifteen 
should  be  able  to  grasp  its  message.  It  handles  its  sub- 
ject from  the  practical  viewpoint  and  covers  every  step 
necessary,  so  that  the  student  who  follows  its  directions 
will  be  able,  by  applying  the  same  in  a  practical  way, 
to  develope  into  an  efficient  worker.  This  statement  is 
made  with  confidence,  for  the  text  has  been  scanned  by 


O^-i- 


some  of  the  most  proficient  men  in  the  optical  world — 
some  of  whom  had  to  discover  through  dear  experience 
the  things  which  are  set  forth  in  this  book  for  the  student, 
who  thereby  has  the  advantage.  However,  self -reliance 
is  golden,  and  self -accomplishment  is  its  twin  faculty. 
The  thing  is  to  master  every  detail. 

In  the  compilation  of  this  volume  its  sponsors  feel 
deeply  indebted  to  these  men  who  HAVE  mastered 
every  detail,  the  exercise  of  whose  grey  matter  has  made 
it  possible  to  pass  along  these  vital  facts  for  the  benefit 
of  the  beginner  through  carefully  scrutinizing  and 
analyzing  its  contents,  and  whose  sanction  pronounces 
it  an  authority  on  its  subject.  They  have  gained  recog- 
nition through  hard  work  and  studious  application  and 
therefore  are  in  themselves  excellent  examples  for  the 
student  to  emulate.  As  our  collaborators  we  wish  to 
thank  '^c'"  (i^d  to  convey  to  you,  dear  student,  our 
appreciation  of  their  co-operation,  in  the  hope  that  you 
may  attain  the  same  proficiency  which  they  possess. 

THE  PROFESSIONAL  PRESS,  Inc. 

Chicago,  Illinois 


!_■■  W 


r    281 


OPTICAL    SHOP    PRACTICE 


Collaborators 


Bcrtolini,    Vincent F.  A.  Hardy  &  Co. 

Brand,  Max  Boston  Optical  Co. 

Brown,  Andrew D.  V.  Brown  Co. 

Bugbee,  L.  W Onepiece  Bifocal  Lens  Co. 

Clements,  Frank  H Globe  Optical  Co. 

Gerue,  William  A Uhlemann  Optical  Co 

Half ord,  Ralph  B Boston  Optical  Co. 

Hallberg,  John  G Interstate  Optical  Co. 

Ingold,  C  F Milwaukee  Optical  Mfg.  Co. 

Kilton,  H Geneva  Optical  Co. 

Knettle,  L.  H Riggs  Optical  Co. 

Lueck,   Edward   J Kryptok  Sales  Co.,  General  Optical  Co. 

Perkins,  John  A Winchester  Optical  Co. 

Robinson,  Erdis Robinson  Optical  Co. 

Sentman,  T.  Frank. Mclntire,  Magee  &  Brown  Co. 

Simetidinger,  Henry  J Julius  King  Optical  Co. 

Smith,    William Geneva  Optical  Co. 

Stevens,   Walter Dempsey-McMann  Optical  Co. 

Troppmann,    C.   J. F.  A.  Hardy  &  Co. 

Weller,   Fred   W Geo.  S.  Johnston  Co. 

Standard  Optical  Co. 


LENS    CUTTING 


CHAPTER  I 

Lms  Cutting 

The  very  first  essential  to  be  mastered  by  the  individual  who  would 
become  proficient  in  cutting  lenses  is  to  learn  to  cut  glass ;  for,  after 
all,  no  matter  whether  a  lens  is  cheap  or  expensive,  it  is  glass. 

The  term  "lens  cutting"  carries  with  it  to  the  mind  of  the  un- 
initiated a  sort  of  mysterious  meaning,  as  indicating  a  difficult  art. 
However,  as  a  matter  of  fact,  anyone  of  ordinary  intelligence  who 
applies  himself  diligently  can  quickly  become  actually  expert  in  cut- 
ting lenses.  Of  course  close  attention  must  be  given  to  instructions 
and  the  latter  must  be  followed  out  carefully,  the  worker  combining 
good  judgment  with  the  faculty  of  placing  himself  under  the  guidance 
of  the  instructor,  for  while  a  thorough  grasp  of  theory  is  excellent, 
yet  the  application  of  the  latter  is  something  which,  to  attain  per- 
fection, requires  practice  and  time. 

There  is  no  necessity  for  an  elaborate,  expensive  set  of  tools  for 
the  beginner,  nor  is  it  necessary  to  follow  any  complicated  method  in 
doing  the  work.  Once  the  primary  principles  have  been  mastered,  the 
rest  is  merely  a  matter  of  care  and  constant  practice. 

The  old  adage,  "make  haste  slowly,"  certainly  applies  in  the 
operation  of  cutting  lenses.  Even  experts  who  have  had  years  of 
practice  know  that  they  cannot  exceed  a  certain  time  limit.  And  the 
only  way  for  the  student  to  become  an  expert  is  by  keeping  "ever- 
lastingly at  it,"  and  by  degrees  he  will  find  himself  becoming  more 
and  more  proficient.  Have  confidence  in  yourself,  and  that  is  a  large 
part  of  the  battle. 

Many  of  the  really  expert  lens  cutters  use  comparatively  simple 
implements  in  doing  the  highest  class  work.  Bear  in  mind  that  in 
learning  to  cut  lenses  you  must  first  learn  the  proper  way  to  cut  glass. 
Use  just  ordinary  window  glass,  which  is  the  best  for  initial  practice. 


10 


OPTICAL    SHOP    PRACTICE 


Window  glass  is  not  expensive  and  can  be  obtained  at  any  paint 
or  hardware  store.  The  thinner  the  glass  that  you  can  get,  the  better. 
Photographic  plates  are  excellent.  By  paying  a  few  cents  extra  you 
can  have  it  cut  at  the  store  in  squares  of  two  inches,  but  the  best  way 
is  to  get  your  hand  in  at  the  beginning  and  cut  the  squares  yourself. 
This  can  be  done  as  follows : 

Buy  any  one  of  the  various  types  of  "glass  cutters,"  which  you 
can  get  at  the  store  where  you  bought  the  glass,  and  which  are  not  at 
all  costly.  An  ordinary  ruler  is  all  you  need  to  lay  the  glass  out  in 
squares.  Dip  the  wheel  of  the  cutter  in  kerosene  or  turpentine ;  then, 
holding  the  cutter  in  the  same  manner  as  you  would  hold  a  pencil, 

proceed  to  cut,  or  mark,  the  glass. 
Then  to  divide  the  glass  into  the 
desired  squares,  hold  the  sheet  up 
a  little  from  the  table  and,  on  the 
oposite  side  from  that  which  you 
have  marked,  follow  the  lines,  for 
instance  those  running  from  right 
to  left,  tapping  gently  just  under 
the  markings.  Then  when  you 
have  the  strips  cut  you  can  obtain 
the  complete  squares  by  repeating 
the  operation  with  them  in  the  same 
way,  always  holding  the  glass  as 
close  as  possible  to  the  table,  so 
that  if  they  fall  they  will  not  break. 
Another  way  to  cut  the  glass  after 
it  has  been  marked  is  to  slide  the 
sheet  toward  you,  resting  it  on  the 
edge  of  the  table  just  over  the  marking  farthest  from  you.  By  raising 
it  and  letting  it  come  down  gently  on  the  edge  of  the  table  you  will 
obtain  the  long  strips.  Do  the  same  thing  with  the  strips  in  securing 
the  squares,  but  always  hegm  with  the  farthest  from  you.  Never  try 
to  "speed  up,"  for  you  will  fail  if  you  do. 

Now  you  have  the  little  squares,  you  are  ready  to  cut  out  the 


LENS    CUTTING 


11 


Actual  sizes  of  lenses  after  being  edged 


12 


OPTICAL    SHOP    PRACTICE 


Actual  sizes  of  lenses  after  being  edged 


LENS    CUTTING  13 

optical  "shapes,"  or  the  forms  of  the  various  lenses  desired.  Here 
again  simple,  inexpensive  tools  are  sufficient.  While  it  is  true  that 
special  tools  for  this  purpose  are  sold  by  the  optical  jobbing  houses, 
we  would  suggest  purchasing  merely  a  hand  cutting  diamond,  or 
pencil  diamond  at  this  stage  of  the  work.  The  other  cutters  will  be 
taken  up  in  proper  time,  after  you  have  become  proficient  and  are 
ready  to  cut  some  of  the  special  and  difficult  forms  that  have  come 
into  use  in  recent  years. 

A  hand  diamond  is  all  that  you  need  at  the  start,  for  with  it 
you  can  cut  anything  desired  and  by  continually  practicing  you  can 
become  a  competent  lens  cutter.  Later  on,  if  you  wish  to  do  so  you 
can  invest  in  a  fifty  or  hundred  dollar  cutting  machine. 

Having  procured  your  cutting  diamond,  there  is  one  other  thing 
that  you  must  have  before  you  can  actually  begin  to  cut  out  the  lenses, 
and  that  is  the  pattern.  Here  again  there  is  not  any  great  expense 
entailed,  for  the  patterns  are  made  of  common  tin  or  celluloid,  such 
as  is  used  in  containers  for  canned  goods  or  tobacco  boxes,  and  you 
can  get  the  material  at  any  tin  shop  or  auto  top  shop.  Out  of  this  you 
can  make  your  own  patterns  for  any  shapes  of  lenses  that  you  wish. 

Get  a  pair  of  ordinary  dividers  at  any  stationery  store,  such  as 
school  children  use,  and  with  them  mark  out  on  the  tin  any  of  the 
round  sizes  you  wish  to  cut — say,  a  42  millimeter.  Then,  with  a  pair 
of  shears,  follow  the  marking  on  the  tin,  keeping  a  little  outside  of 
it  about  one  millimeter,  so  that  the  pattern  will  measure  43,  instead 
of  42  millimeters.  You  will  find  that  the  ^dge,  of  the  pattern  is  left 
more  or  less  rough,  and  you  can  smooth  this  down  with  a  file,  exercis- 
ing care  to  make  the  edge  uniform  and  smooth,  and  keeping  right  on 
the  original  mark.  Do  not  overlook  the  fact  that  if  there  is  the  least 
roughness  on  the  pattern  it  may  scratch  the  lenses,  or  glass,  which 
you  are  about  to  cut.  You  can  make  patterns  for  any  other  types 
of  lenses,  of  course,  such  as  long  oval,  short  oval,  drop  oval  or  leaf 
shape,  etc.,  by  marking  and  cutting  as  before,  only  not  with  the  di- 
viders. 

The  stationary  leg  of  the  dividers  will  mark  the  center  of  the 


14  OPTICAL    SHOP    PRACTICE 

round  shape  by  a  little  indentation.  Make  a  scratch  through  this 
center  and  running  to  the  edges;  then  make  another  scratch  through 
the  center,  crossing  the  first  one  at  right  angles.  Now  punch  a  hole 
(about  2  milHmeters  in  diameter)  through  the  center  thus  established, 
and  file  down  the  ragged  edges  after  making  the  hole.  The  reason 
for  making  this  hole  in  the  center  and  marking  the  lines  at  right 
angles  on  the  pattern  is  that  all  optical  lenses  are  "centered,"  and  a 
small  ink  dot,  or  dots  on  the  lens  is  for  the  purpose  of  showing  the 
"optical  center."     This  point  will  be  dealt  with  later  on. 

Now  you  have  the  necessary  tools  and  material  for  cutting  your 
lens — ^the  diamond,  pattern  and  "blank,"  or  the  square  of  glass  from 
which  the  lens  is  to  be  cut. 

You  next  take  your  "practice  piece"  of  window  glass ;  find  the  exact 
center  and  place  there  an  ink  dot.     Any  waterproof  ink  will  do,  and 

for   making   the   dot   an   ordinary 

toothpick  is  better  than  a  pen.  Then 

place  the  pattern  on  the  glass  so 
that  the  hole  in  the  center  of  the 
pattern  will  be  over  the  dot  on  the 
glass.  Hold  them  tightly  together 
with  the  first  two  fingers  of  the 
left  hand  (assuming  that  you  are 
not  left-handed)  under  the  glass, 
and  the  left  thumb  on  top  of  the 
tin  pattern,  so  that  the  pattern  will 
not  slip. 

Now  place  the  part  of  the  glass 
farthest  from  you  on  the  edge  of 
the  bench  (which  should  be  covered  with  a  mat  of  rubber  or  thick 
blotting  paper)  and  draw  the  point  of  your  diamond  around  the  pat- 
tern— only  half  zvay.  Then  still  keeping  the  glass  and  pattern  held 
firmly  together,  turn  them  half  way  round  and  mark,  or  cut,  the 
other  half.  Be  careful  not  to  let  your  mark,  or  cut,  overlap  the  first 
one,  as  you  may  spoil  the  diamond.     The  amount  of  pressure  to 


LENS    CUTTING 


15 


exert  in  cutting  is  governed  by  the 
cutting  edge  of  the  diamond.  You 
will  learn  this  by  experimenting  with 
pieces  of  glass.  A  very  sharp  dia- 
mond will  only  require  light  pressure, 
while  the  duller  the  cutting  edge  the 
greater  the  pressure  needed.  Con- 
tinued practice  will  teach  you.  Now, 
in  order  to  liberate  the  lens  which 
you  have  cut  from  the  two-inch 
square,  mark  lines  with  the  diamond 
from  the  edge  of  the  square  close  to 
the  edge  of  the  desired  lens,  and  not 

at  right  angles  to  the  lense  edge,  but  on  a  tangent,  as  indicated  by  the 

diagram. 

Always  hold  the  diamond  at  right  angle  to  the  surface  of  the  lens ; 

see  that  the  flat  place  where  diamond  is  set  be  parallel  to  the  edge  of 

pattern. 

Having  now  learned  the  principles  of  lens  cutting,  you  are  ready 

for  the  next  step  in  the  work,  which  is  lens  chipping. 

Quiz 

1 — What  tools  are  required  at  first? 

2 — What  kind  of  glass  is  best  for  practice?  To  what  size  should  it  be 
cut  for  practice  work? 

3 — What  tool  do  you  use  for  cutting? 

4 — What  do  you  do  to  make  it  cut  if  the  point  is  sharp?     If  dull? 

5 — From  what  material  are  patterns  made? 

6 — What  do  you  use  to  mark  the  pattern?     To  cut  it? 

7 — What  should  you  do  to  the  edge  of  the  pattern?     Why? 

8 — How  do  you  make  it  smooth? 

9 — What  do  you  do  to  the  center  of  the  pattern? 

10 — Why  should  you  dot  the  glass?     What  kind  of  ink  is  necessary? 

11 — What  is  best  to  use  with  the  ink  in  dotting  lenses? 

12 — How  do  you  hold  the  glass  and  pattern? 

13 — With  what  should  the  edge  of  the  bench  be  covered? 

14 — How  do  you  place  the  lens  on  the  bench? 

15 — How  do  you  mark  the  lens,  as  to  cutting? 

16 — Is  it  all  right  to  let  the  markings  of  the  two  halves  of  the  lens  over- 
lap?    If  not,  why  not? 

17 — With  the  lens  outlined,  how  do  you  release  it  from  the  rest  of  the 
glass  "blank"? 


16  OPTICAL    SHOP    PRACTICE 


CHAPTER  II 

Lens  Chipping 

Chipping  lenses  is  another  operation  in  lens  cutting  which  appears 
to  the  beginner  to  be  harder  than  it  really  is  in  actual  practice.  While 
the  work  itself  is  not  difficult,  nevertheless  it  requires  the  same  degree 
of  careful  attention  that  is  necessary  to  become  an  efficient  lens  cutter. 
Here  again  considerable  time  should  be  given  to  experimenting  on 
common  window  glass,  and  the  student  should  not  attempt  to  work 
on  optical  lenses  until  he  has  acquired  complete  confidence  in  his 
ability  to  hold  the  lens  so  that  he  does  not  have  to  think  too  much 
about  it;  until  he  knows  without  stopping  to  think  just  how  much 
pressure  to  exert.  In  short,  the  student  must  acquire  the  "knack" 
of  doing  the  work  so  that  he  can  perform  the  various  little  operations 
almost  unconsciously. 

The  old  saying,  'There  are  tricks  in  all  trades,"  applies  in  both 
cutting  and  chipping  lenses.  Gradually,  as  the  student  becomes  more 
adept  through  continued  practice,  the  different  operations  will  come 
so  easily  that  he  will  not  have  to  think  about  them.  It  will  be  "second 
nature"  to  him. 

In  chipping  jjlass,  the  first  thing  to  learn  is  how  to  hold  the  lens 
properly.  This  is  done  in  very  much  the  same  way  that  the  worker 
holds  the  glass  blank  and  pattern  as  described  in  the  last  chapter  in 
the  operation  of  lens  cutting,  or  marking,  the  glass  being  held  with 
the  first  two  fingers  underneath  and  the  thumb  on  top,  but  closer  to 
the  diamond  mark,  so  as  to  avoid  leverage,  which  would  cause  the 
risk  of  breakage.    In  this  way  a  firm  grip  is  gained  and  there  is  less 


LENS    CHIPPING 


17 


chance  that  the  glass  will  slip.  After 
practicing  a  few  times  with  a  piece 
of  window  glass  you  will  learn  the 
right  amount  of  pressure  to  use  in 
order  to  hold  the  glass  firmly,  yet 
easily,  after  which  this  part  of  the 
work  will  be  really  automatic  on  the 
part  of  the  student. 

In  chipping,  the  pliers  are  held 
in  the  same  manner  that  one  would 
hold  any  other  pliers — common  wire 
pliers,  for  instance.  However,  be- 
ginners often  make  one  great  mistake, 
in  thinking  that  the  pliers  are  intended 
to  "pinch"  the  glass.  Never  pinch  the 
glass  hard. 

Having  marked,  or  cut  the  shape  in  the  glass  as  described  in  the 
last  chapter  and  then  scored  the  tangent  lines,  hold  the  piece  between 
the  thumb  and  first  two  fingers,  as  directed  (with  the  scored  or 
scratched  side  up)  and  with  the  chipping  pliers  begin  to  chip  off  the 
useless  pieces,  beginning  at  the  comers.  Remember — do  not  pinch 
hard.  And  do  not  try  to  chip  off  too  much  at  a  time.  Holding  the 
glass  firmly,  take  a  light,  easy  grip  at  the  corner  with  the  pliers  and 
then  turn  the  wrist  slightly  downward.  Keep  moving  the  glass  as 
you  chip,  and  be  very  careful  as  you  get  near  the  mark  that  you 
previously  made. 

At  first  the  experimental  work  of  chipping  should  be  with  very 
thin  glass.  After  the  student  has  worked  for  a  few  hours  at  this  he 
should  try  thicker  glass — say,  four  or  five  millimeters  in  thickness. 
Here,  as  in  cutting,  make  haste  slowly.  Speed  will  come  with  the 
confidence  which  careful  practice  will  create. 

It  might  be  well  here  to  refer  to  lens-cutting  machines.  Quite  a 
number  are  on  the  market,  and  any  optical  jobber  will  gladly  furnish 


18 


OPTICAL    SHOP    PRACTICE 


anyone  with  a  complete  list,  together  with  the  prices  at  which  the 
machines  are  sold.  We  do  not  recommend  any  particular  kind,  as  it 
is  entirely  a  matter  of  getting  the  particular  kind  which  the  worker's 
judgment  selects  and  then  in  getting  thoroughly  familiar  with  it; 
learning  how  it  is  constructed,  all  the  details  of  the  mechanism  and 
how  to  set  the  machine  for  the  different  sizes.  Here,  as  in  other 
kinds  of  skilled  work,  personal  opinion  is  the  determining  factor. 
Some  operators  will  use  a  hand  diamond  for  years  and  claim  it  is 
the  only  perfect  tool,  while  others  will  use  it  for  an  hour  or  so  and 
throw  it  aside  as  virtually  useless. 

Quiz 

1 — What  is  the  first  thing  to  learn  in  chipping? 
2 — How  do  you  hold  the  glass? 
3 — Must  you  use  much  pressure  with  the  pliers? 
4 — Where  do  you  begin  to  chip? 


THE  FOUNDATION 
of  Every  Trade  or  Pro- 
fession   is    Based  on    Theory   and 
Practice.      Those  Desiring  to  Reach 
the  Top  Strive  for  More  Knowledge  from  the  Writ- 
ings of  THOSE  WHO  HAVE  REACHED  THE 
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TIHIE   OFTOilETIRIIO   WEEBCLY 


LENS    EDGING  19 


CHAPTER  III 

Lens  Edging 

The  first  step  in  lens  edging  is  to  train  the  eye  to  "see"  the  several 
shapes.  That  is  to  distinguish  one  from  the  other  at  a  glance;  or,  in 
other  words,  to  visualize,  to  form  a  mental  picture  of  a  true  form  of 
an  oval,  or  any  other  shape  mentioned  or  required.  The  second  step 
is  to  train  the  fingers  and  hands  to  hold  the  lens  in  the  correct  position 
and  at  the  proper  angle,  also  to  give  it  the  proper  amount  of  pressure 
against  the  stone. 

You  have  already  learned  the  importance  of  chipping  the  lens 
down  as  closely  as  possible  to  the  cut-mark,  for  the  purpose  of  getting 
all  the  "bumps"  or  sharp  corners  off,  to  avoid  scratching  the  surface 
of  the  grinding  stone,  because  doing  this  makes  less  work  in  grinding 
the  lens  to  the  required  shape  and  is  a  great  time  saver.  When  you 
have  learned  this  thoroughly;  when  your  eye  has  been  trained  to 
instantly  visualize  the  different  shapes  of  lenses;  when  your  fingers 
and  hands  are  also  trained  to  instantly  place  the  lens  in  the  correct 
position  and  apply  the  right  amount  of  pressure^ — then  you  are  ready 
for  the  next  step,  which  is  the  selection  and  operation  of  the  grinding 
stone. 

Right  here  bear  one  thing  in  mind — Never  waste  time  and  money 
on  second-hand  stones.  Write  to  any  reputable  wholesale  house  and 
have  them  send  you  a  perfect  stone,  mounted  on  a  bench  or  stand, 
as  you  may  wish.  These  stones  have  been  thoroughly  tested  and 
leave  the  factory  in  perfect  shape,  ready  for  use  as  soon  as  they  are 
set  up  and  the  power  is  turned  on.  The  manufacturers  of  these  stones 
will  stand  behind  their  products,  and  you  can  proceed  with  the  assur- 
ance that  each  stone  will  give  loo  per  cent  service  if  you  do  your 
part  intelligently  and  efficiently. 


20 


OPTICAL    SHOP    PRACTICE 


Now  you  come  to  a  part  which  requires  the  exercise  of  that  all- 
important  factor  known  as  common  sense,  combined  with  lots  of 
patience  and  careful  attention  to  the  instructions  given  you,  as  well 
as  the  small  details  which  are  a  part  of  this  work. 


Edging  Beveled  Lenses 

First  you  must  learn  to  hold  the  lens  properly.  Take  it  firmly 
between  the  first  finger  and  thumb  of  both  hands,  pressing  it  lightly 
against  the  stone,  and  at  the  same  time  turning  it  half  way  round  and 
feeding  it  toward  the  right,  tilting  it  slightly  so  as  to  produce  a  bevel 
edge  at  an  angle  of  45  degrees  to  the  surface  of  the  glass  and  extending 

half  way  across  the  thickness  of 
the  glass.  Do  the  same  with  the 
other  half  of  that  edge.  Then  turn 
the  glass  over  and  repeat  the  oper- 
ation on  the  other  side  of  the  edge 
of  the  lens,  so  that  the  bevel  thus 
produced  will  be  at  right  angles  to 
the  first,  or  90  degrees,  and  this 
will  give  the  edge  of  the  lens  a 
wedge-shape,  or  V-shape. 

Now  hold  the  lens  between  the 

thumb    and    middle    finger    firmly 

and  place  the  first  finger  on   the 

apex  of  the  angle  formed  by  the 

two  bevels,  for  you  are  ready  to 

''touch  off,"  or  for  "running  off,"  the  edge,  or  apex,  produced  by  the 

last  operation,  so  as  to  avoid  chipping  the  lens  when  drawing  the  end 

pieces  of  the  frame  together. 

In  other  words,  let  us  repeat.  Remove  the  humps  or  sharp  points 
if  there  are  any  left  from  cutting  the  lens.  Then  you  must  hold  the 
lens  properly,  rest  it  upon  the  first  finger  of  left  hand,  place  the  thumb 
of  right  over  it  using  just  enough  pressure  to  keep  from  slipping.  Now 
push  the  lens  away  from  you  slowly  with  left  thumb,  follow  this  up  by 


LENS    EDGING  21 

pulling  the  lens  toward  you  with  the  first  finger  of  right.  Practice  this 
until  you  can  rotate  the  lens  slowly  and  smoothly  away  from  the  stone. 
After  you  master  this  motion,  place  the  lens  upon  the  stone  at  desired 
angle  about  45°,  and  as  you  rotate  your  lens,  press  more  firmly  against 
the  stone  at  the  thick  parts  or  the  point  where  more  material  has  to 
be  removed  to  form  a  perfect  oval. 

Edging  Rimless  Lenses 

Your  previous  experience  will  by  this  time  teach  you  the  proper 
amount  of  pressure  to  exert  in  holding  the  edge  against  the  stone,  the 
lens  now  being  held  perpendicular.  Turn  the  lens  in  the  direction  in 
which  the  stone  is  revolving.  The  ability  to  do  this  correctly  will 
come  to  you  easily,  with  constant  practice.  Go  at  this  process  slowly. 
Even  the  best  operators  do.  When  you  have  finished  this  you  will 
have  produced  a  "rimless"  lens.  However,  remember  one  thing — 
stick  to  the  ordinary  oval  lens  and  the  window  glass  oval  at  first,  for 
by  mastering  work  on  this  the  rest  will  come  to  you  easily.  Mastering 
of  these  details  will  come  with  practice.  There  is  nothing  difficult  in 
edge-grinding,  it  is  merely  the  exercise  of  judgment  and  care  combined 
with  continued  practice,  and  once  you  have  mastered  work  on  the 
oval  lens,  operations  on  the  other  shapes  will  be  comparatively  easy. 
Do  not  become  discouraged  if  the  "knack"  of  doing  this  work  docs 
not  come  to  you  quickly.    Just  keep  at  it. 

As  soon  as  you  have  mastered  the  principles  involved  in  the  work 
of  edge-grinding,  it  is  a  good  idea  to  dwell  a  little  upon  what  kind  of 
implements  are  the  best  to  use,  together  with  the  care  that  they  should 
be  given.  ^  .  /        , 

Nearly  always  the  first  question  that  occurs  to  the  student's  mind 
is  just  what  size  stone  is  best  for  general  work  and  at  what  speed  it 
should  be  operated.  As  a  general  proposition  a  stone  24  inches  in 
diameter  and  13^  inches  thick  and  run  at  a  speed  of  200  to  250  revo- 
lutions per  minute  will  be  found  practical  and  sufficient. 

One  of  the  best  stones  is  a  manufactured  abrasive  bonded  together 


OPTICAL    SHOP    PRACTICE 


©©000 

00©©© 


©©©00 


LENS    EDGING  23 

so  as  to  produce  a  stone  of  the  above  dimensions.  This  is  a  fast- 
cutting  stone,  one  of  the  very  best  on  the  market,  and  requires  very 
Httle  attention,  especially  if  handled  properly.  It  is  a  "composition 
stone,"  and  it  is  usually  recommended  in  preference  to  others. 

Proper  care  of  the  stone  is  a  very  important  factor  in  edge  grind- 
ing, no  matter  what  type  is  used.  You  will  find  in  your  work  that 
a  large  amount  of  soft,  white,  mushy  matter  is  deposited  around  the 
stone.  This  consists  of  ground  glass,  stone  and  water  and  should 
be  wiped  off  carefully  every  day,  and  all  metal  parts  of  the  equipment 
should  be  wiped  with  a  rag  saturated  with  gasoline,  benzine  or  kero- 
sene. This  is  very  important.  Don't  put  this  off  "till  tomorrow." 
Do  it  today. 


Formers  for  Lense  Edging. 

There  are  several  kinds  of  automatic  machines  on  the  market, 
all  of  them  operated  in  a  similar  way  and  having  about  the  same  kind 
of  equipment — a  holder  to  contain  the  lenses  before  they  are  put  into 
the  machine,  a  clasp  to  keep  them  in  position,  and  a  spring  to  give 
the  proper  tension  and  a  plate  to  give  the  size  required.  Directions 
in  full  are  given  with  all  machines. 

Automatic  edging  machines  are  very  valuable  where  large  quan- 
tities of  lenses  are  to  be  edged,  and  any  intelligent  person  can  operate 
six  or  eight  of  them  at  one  time.  However,  it  has  been  demonstrated 
that  in  the  long  run  the  experienced  hand-edger  can  do  the  work  in  a 
more  satisfactory  manner,  as  he  is  familiar  with  the  amount  of  tension 
that  is  necessary  and  which  is  exercised  by  the  tension  spring  in  the 
machine,  so  as  to  give  the  right  degree  of  pressure,  and  it  is  only 
logical  to  assume  that  the  experienced  hand-edger  would  use  more 
caution  than  someone  not  having  had  this  experience  and  would  pro- 
duce better  results. 

Before  attempting  to  operate  an  automatic  machine,  the  beginner 
should  go  through  a  course  of  practice,  using  common  window  glass. 


24  OPTICAL    SHOP    PRACTICE 

This  will  enable  him  to  acquire  the  "knack"  and  will  prepare  him  for 
work  on  actual  optical  lenses. 

There  is  a  wide  range  of  prices  of  automatic  edging  machines 
and  all  large  optical  houses  carry  machines  in  stock.  With  each 
machine  comes  a  ibook  of  instructions  explaining  in  detail  all  working 
parts,  how  to  care  for  the  machine,  together  with  all  other  necessary 
information,  including  that  pertaining  to  size  and  shapes  of  lenses,  etc. 

Every  beginner  is  strongly  urged  to  'become  proficient  at  hand 
edging,  even  though  he  intends  to  work  mostly  on  automatic  machines, 
for  there  are  so  many  odd  sizes  and  shapes  of  lenses  that  cannot  be 
edged  on  the  automatic  machines — such  as  half-eyes,  clerical  and 
crescent  shapes,  etc.  After  you  have  once  mastered  edging  on  oval, 
all  other  shapes  will  be  easy  for  you. 

To  keep  the  grinding  face  of  the  stone  in  perfect  condition:  All 
automatic  machines  are  equipped  with  a  truing  device  consisting  of 
a  carborundum  stone  fixed  in  a  sliding  rest.  This  should  be  used 
whenever  the  stone  gets  out  of  true  or  when  slight  grooves  appear 
on  its  face. 

Small  grooves  will  often  appear  on  hand  edging  stones,  but  these 
can  be  taken  out  very  easily  by  the  following  method:  buy  a  small 
carborundum  stone  at  any  hardware  store,  or  a  piece  of  pebble  or  glass, 
also  make  it  wet,  and  hold  this  against  the  face  of  the  grinding  stone, 
moving  it  sidewise  across  the  face  of  the  stone.  Follow  this  with  a 
piece  of  old  glass,  using  the  same  kind  of  movement,  and  within  a 
short  time  the  stone  will  be  flat  and  smooth  and  ready  for  good  work. 

Fitting  Zylo  Rims 

Fitting  zylo  rims  to  lenses:  Most  expert  edge  grinders  select  a 
rim  about  i  millimeter  smaller  than  the  circumference  of  the  lens 
after  it  is  edged  correctly.  Heat  is  required,  in  order  to  stretch  the 
zylo,  but  no  flame  should  ever  be  permitted  to  come  into  contact  with 
it.    Hot  water  (not  boiling),  hot,  dry  asbestos  or  a  little  electric  stove 


LENS    EDGING 


25 


will  furnish  sufficient  heat  to  make  the  rim  pliable,  when  it  can  be 
stretched  over  the  lens.  Where  a  small  rim  is  to  be  fitted  over  a  large 
lens  get  a  wooden  mandrel,  heat  it  and  slip  the  rim  over  it.  There 
are  many  so-called  "rim  stretchers"  on  the  market  and  sold  at  various 
prices  by  the  optical  houses.  The  jobbers  will  supply  you  with 
information  regarding  them.  When  the  rim  has  been  placed  on  the 
lens  spray  cold  water  on  it,  so  that  it  will  cool  readily,  thus  contract- 
ing, or  shrinking,  and  making  a  tight  "fit.'* 


Fitting  Metal  Frames 

To  fit  beveled  lenses  into  metal  frames:  Whether  the  material  of 
the  frame  be  gold,  gold-filled  or  any  other  metal,  the  principal  require- 
ment in  fitting  lenses  into  such  frames  is  more  of  the  common  sense 
to  which  we  have  already  referred.  After  edging  the  lense  down,  fit 
it  into  the  frame  by  pulling  the  two  end  pieces  together  with  a  dull  pair 
of  cutting  pliers.  Take  great  care  in  this  operation,  as  too  much  pres'- 
sure  will  chip  the  lens  if  it  is  too  large.    Try  the  lens  in  the  eye  wire 

several  times,  us- 
ing great  care 
when  the  lens  is 
about  the  right 
size.  It  is  better 
for  the  lens  to  be 
made  too  large 
than  either  the  ex- 
act size  required 
or  too  small,  as  in 
the  first  case  the  lens  can  be  cut  down,  while  if  it  is  the  exact  size 
it  may  be  damaged  a  little  and  will  not  permit  cutting  down,  while  if 
it  is  too  small  in  the  first  place  it  cannot  be  used  for  the  frame,  for 
being  small  it  would  move  a  cylindrical  lens  in  the  frame,  and  the 
axis  would  be  wrong. 


26  OPTICAL    SHOP    PRACTICE 

Quiz 

1 — What  is  the  first  step  in  edging?    The  second  step? 

2 — Why  is  it  important  to  chip  the  lens  close  to  the  cut  mark  ? 

3 — Why  is  the  stone  so  important? 

4 — How  do  you  hold  the  lens  in  beveling?  Describe  the  operation  of 
beveling. 

5 — What  is  a  rimless  lens? 

6 — Why  should  you  stick  to  the  oval  type  so  long? 

7 — What  is  the  best  size  stone  to  get  ?    At  what  speed  should  it  be  operated  ? 
8 — How  often  should  you  clean  the  stone?    Why? 

9— When  are  automatic  machines  used?  Which  is  most  satisfactory — hand 
edging  or  machine?    Why? 

10 — ^Why  should  every  beginner  become  an  efficient  hand-edger,  even 
though  intending  to  operate  an  automatic  machine? 

11 — How  do  you  keep  the  face  of  the  stone  in  perfect  condition? 

12 — How  do  you  fit  zylo  rims  on  lenses? 

13 — How  do  you  fit  beveled  lenses  in  metallic  frames? 

14 — Is  it  advisable  to  have  the  lenses  the  same  size?  Smaller?  Larger? 
Give  reasons  in  each  case. 


The  Reliable  Magazine  Has  Become  Part  of  the  Mod- 
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comer Follows  the  Veteran,   and  the 
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WEEKLY 


DRILLING    AND    MOUNTING    LENSES 


27 


CHAPTER  IV 

Drilling  and  Mounting  Lenses 

The  drilling  of  lenses,  just  as  the  other  operations  already  dealt 
with,  is  a  process  which  can  only  be  mastered  gradully,  to  which  end 
the  individual  must  be  patient,  persevering  and  not  afraid  to  put  in 
plenty  of  time  practicing,  so  that  he  will  get  the  various  little  tricks 
and  turns  that  will  eventually  make  him  proficient. 

A  complete  line  of  lens  drills  is  manufactured  for  the  trade  and 
nearly  all  are  fitted  with  diamond  points  and  also  with  adjustable 
mechanism  for  keeping  the  diamond  from  touching  the  metal  rest. 
Adjustments  are  also  provided  so  that  the  hole  can  be  drilled  close  to 
or  away  from  the  edge  of  the  lens.     Full  information  regarding  any 

lens  drill  on  the  market  can  be  had 
from  any  optical  jobbing  house. 

The  average  speed  at  which  the 
drill  should  rotate  is  from  1,900  to 
2,500  revolutions  per  minute,  and 
to  operate  them  it  takes  about  one- 
eighth  horsepower. 

Practically   all    drills    are   fitted 
with    an    adjustable   table   so   ar- 
ranged that  the  lens  can  be  turned 
to  allow  a  hole  to  be  drilled  above 
or  below  the  center.    They  can  also  be  tilted,  for  drilling  toric  lenses. 

A  "drilling  fluid"  must  always  be  used  during  the  entire  opera- 
tion of  drilling.  Experience  has  shown  that  one  of  the  best  drilling 
fluids  is  made  of  common  turpentine  and  "3-in-i"  oil,  mixed  in  the 
ratio  of  four  parts  of  turpentine  to  one  of  the  oil.  A  small  camel 
hair  brush  should  be  used  to  apply  the  fluid  while  the  drilling  is  being 
done.    However,  the  latest  drills  have  automatic  oil  feeds. 


28  OPTICAL    SHOP    PRACTICE 

The  amount  of  pressure  exerted  during  the  drilling  is  a  very 
important  factor.  It  is  a  good  rule  to  use  the  smallest  amount  prac- 
ticable, until  you  have  learned  your  drill  thoroughly. 

The  lens  should  never  he  drilled  clear  through  from  one  side. 
Set  the  adjustment  on  the  machine  so  that  the  drill  will  go  only  half- 
way through  the  lens;  then  reverse  the  work  and  finish  drilling  the 
hole  from  the  side  opposite  that  on  which  you  started.  As  soon  as 
the  two  holes  meet  stop  drilling.  lAs  you  become  accustomed  to  the 
sound  of  the  drilling  your  ear  will  become  trained  so  that  you  will  be 
able  to  detect  within  almost  the  fraction  of  a  second  when  to  release 
the  pressure.  i         .    !  '    ;  ^  f  ^ 

It  is  a  good  idea  to  release  the  drill  frequently  and  apply  plenty 
of  drilling  fluid  over  the  hole  with  the  camel  hair  brush. 

One  thing  to  be  borne  in  mind  is  the  fact  that,  as  a  general  rule, 
the  holes  in  lenses  should  be  drilled  at  right  angles  to  the  curvature  of 
the  lenses,  and  the  "chuck"  on  your  drill  must  be  set  accordingly. 
Unless  specified  otherwise  in  the  prescription,  the  lens  should  generally 
be  drilled  on  the  center.  Read  the  prescription  very  carefully  and 
follow  it  closely  in  regard  to  special  instructions  relating  to  the  way 
it  should  be  drilled. 

When  the  hole  has  been  made  from  each  side  of  the  lens,  you 
will  note  that  it  is  small  at  the  center  and  wider  at  the  surfaces.  In 
order  to  get  it  the  same  size  all  the  way  through  it  will  be  necessary 
to  use  a  reamer.  All  drills  are  provided  with  reamers.  Put  plenty 
of  fluid  on  the  point  of  the  reamer  while  applying  the  lens  in  a  vertical 
position  as  you  press  it  on  the  reamer,  touching  the  reamer  constantly 
with  the  brush  during  the  operation.  If  you  are  careful  to  keep  the 
lens  in  a  true  upright  position  and  the  reamer  in  a  true  horizontal 
position  you  will  get  a  perfect  hole. 

The  drill  must  always  be  kept  clean,  for  otherwise  the  drilling 
fluid  will  get  into  the  parts  and  become  gummy.  Either  gasoline  or 
benzine  is  excellent  for  this  purpose. 

Always  make  sure  when  you  use  a  new  drill  point  or  diamond 


DRILLING    AND    MOUNTING    LENSES  29 

to  see  that  it  is  a  perfect  fit,  and  while  it  is  running  take  great  care 
that  it  does  not  vibrate  laterally,  or  "chatter"  as  it  is  termed.  In  other 
words,  the  drill  should  turn  perfectly  parallel  with  its  axis  and  operate 
smoothly  and  silently,  except  when  the  point  is  in  contact  with  the 
work.  Lateral  vibration  has  a  tendency  to  turn  the  work,  which  often 
results  in  breakage.  If  you  are  careful  to  keep  your  drill  in  perfect 
condition  you  will  go  far  toward  turning  out  perfect  work. 

A  medium  short  diamond  will  be  found  the  best  for  average  work, 
as  it  will  give  longer  and  better  service.  Nearly  all  optical  drills  come 
fitted  with  white  diamonds,  but  it  is  a  very  good  precaution  to  have 
an  extra  point,  so  that  if  the  one  you  have  should  get  broken  you  will 
have  the  other  at  hand  and  thus  save  valuable  time.  When  the  drill 
becomes  dull  send  the  point  back  to  the  wholesale  house,  to  be  sharp- 
ened. The  jobber  knows  the  best  place  to  have  this  done  and  you 
will  find  in  the  long  run  that  this  is  the  most  economical  way  of  having 
the  matter  attended  to. 

There  are  hand  drills  on  the  market,  but  the  use  of  these  entails 
so  much  time  that  it  would  not  be  good  policy  to  use  ope.  As  in 
every  other  line  of  mechanical  work,  time  is  a  big  factor  in  this  one. 

Mounting  Rimless  Lenses 

To  the  beginner  the  mounting  of  rimless  lenses  in  finger  piece 
and  spectaoJe  mounting  is  not  a  difficult  operation.  In  order  to  obtain 
good  results,  the  following  tools  are  necessary :  A  pair  of  strap  pliers, 
simple  nose  pliers,  cutting  pliers,  a  rat-tail  file,  taps  and  tap  holder, 
pin  vise,  a  good  rimless  screwdriver,  a  flat  file,  a  bottle  of  glass  screws, 
a  bottle  of  drilling  fluid.  It  is  a  very  important  matter  that  special  at- 
tention be  paid  to  the  matter  of  fitting  the  strap  to  the  lens.  The  straps 
must  lie  flush  with  the  lens  and  should  be  bent,  to  conform  *to  the 
convexity  of  the  lens.  The  straps  are  not  hard  to  bend.  The  proper 
way  is  to  make  the  straps  either  a  little  wider  or  narrower,  as  the  case 
may  be. 

After  getting  the  strap  to  fit  the  lens,  always  tap  out  the  threads, 


30  OPTICAL    SHOP    PRACTICE 

so  as  to  get  the  straps  in  line.  Never  try  to  force  a  screw  through  the 
straps  and  lens  until  you  have  run  your  tap  through;  see  that  it  runs 
through  freely,  for  if  there  is  the  least  binding  you  can  almost  always 
look  for  a  chipped  or  broken  lens.  The  utmost  care  should  be  used 
in  drilling.  See  that  the  holes  are  not  too  far  forward  or  back.  In 
case  the  hole  is  too  far  in,  it  will  be  a  case  of  filing  the  hole  nearer 
the  edge.  If  the  hole  is  too  near  the  edge  it  will  mean  bending  the 
shoulder  up,  and  this  is  not  a  good  way,  for  the  lens  will  work  loose 
very  quickly. 

The  beginner  should  use  old  lenses  to  practice  upon  and  try  to 
select  several  different  thicknesses.  A  few  hours  should  be  spent 
every  day  practicing  this  work  before  you  attempt  to  mount  any  of 
the  expensive  lenses.  To  do  the  work  perfectly  it  requires  a  good  set 
of  tools,  and  it  should  be  the  aim  of  the  beginner  to  exercise  the 
greatest  patience  in  order  to  accomplish  good  results. 

Quiz 

1 — With  what  kind  of  points  arc  most  drills  fitted? 

2 — ^Why  are  power  drills  the  best?  What  is  the  best  average  speed  for 
same  ? 

3 — Why  does  the  drill  have  an  adjustable  table? 

4 — Why  should  drilling  fluid  be  used? 

5 — How  is  drilling  fluid  made?    In  what  proportions?     How  applied? 

6 — What  amount  of  pressure  is  required  in  drilling? 

7— How  far  should  you  drill  through  from  each  side?  How  can  you  tell 
when  the  holes  meet? 

8 — In  practice,  what  precaution  should  be  taken? 

9 — What  tool  should  be  used  to  make  the  hole  perfect?  What  is  used  to 
lubricate  this  tool? 

10— How  is  the  reamer  operated?  In  what  position  should  the  lens  be  held 
for  reaming? 

11 — In  what  position  should  the  reamer  be  held? 

12--Why  should  the  drill  be  kept  clean? 

13— What  should  be  used  to. clean  the  drill?  '        I 

14 — ^What  is  likely  to  cause  breakage? 


OPTICAL    LENSES 


31 


CHAPTER  V 

s  Optical  Lenses 

Optical  lenses  are  of  many  kinds  and  usually  come  from  the 
manufacturer  finished  on  both  sides,  so  that  no  other  work  is  neces- 
sary except  to  cut  and  edge,  other  than  in  usual  corrections. 

Finished  lenses  are  always  packed  in  individual  envelopes  or 
containers,  and  come  marked  according  to  the  focus.  The  following 
are  a  few  of  the  many  terms,  with  their  meaning,  used  in  the  craft, 
and  it  is  advisable  for  the  beginner  to  become  thoroughly  familiar 
with  the  different  kinds  of  lenses  and  their  nomenclature. 


D  C  X  means  double  convex. 


D  C  C  means  double  concave. 


PCX  (periscopic  convex)  always  has  a 
1.25  curve  on  the  inside. 


P  C  C  (periscopic  concave)  always  has  a 
+  1.25  curve  on  the  outside. 


Meniscus  C  X  means  deep  convex  spher- 


ical. 


Meniscus  C  C  means  deep  concave  spher- 


ical. 


32  OPTICAL    SHOP    PRACTICE 

Lens  Terms  and  Their  Meaning 

PCX  lenses.  All  P  C  X  lenses  are  ground  to  a  — 1.25  curve  on 
the  inside,  while  the  opposite  side  has  any  curve  that  you  may  desire. 
For  example,  a  P  C  X  i.oo  would  be  ground  +2.25  on  the  outside  and 
— 1.25  on  the  insidCj  as  follows: 

+2.25—1.25. 

Example:  a  P  C  X  4.00  would  be  ground  +5.25 — 1.25. 

P  C  C  lenses.  All  P  C  C  lenses  are  ground  +1.25  curve  on  the 
outside  and  any  curve  that  you  may  wish  on  the  inside,  or  opposite 
side.    For  example:  a  P  C  C  1.25  would  be  +1.25  — 2.50.    , 

Example:  a  P  C  C  3.50  would  be  +1.25  — ^4.75. 

The  Meniscus  C  X  lens.  All  meniscus  C  X  lenses  are  ground 
— 6.00  on  the  inside  and  any  curve  desired  on  the  outside.  For  example : 
a  meniscus  C  X  i.oo  would  be:  +7.00  — 6.00. 

Example:  a  meniscus  C  X  4.50  would  be:  +10,50  — 6.00. 

The  Meniscus  C  C  lens.  All  meniscus  C  C  lenses  as  a  rule  are 
ground  +6.00  on  the  outside  and  any  desired  curve  on  the  inside.  For 
example:  a  meniscus  C  C  1.25  would  be:  +6.00  — ^7.25. 

Example :  a  meniscus  C  C  3.75  would  be :  -f  6.00  — 9.75. 

The  Plano-toric  C  X  cyls.  All  plano-toric  C  X  cyls.  are  ground 
with  two  curves  on  the  convex  side  and  a  — 6.00  curve  on  the  opposite 
side.    Example :  Plano-toric  C  X  cyl.  .50 :  +6.00  +6.50  —6.00 

Example:  Plano-toric  C  X  cyl.  1.50:  +6.00  +7.50  — 6.00. 

The  Plano-toric  C  C  cyl.  All  plano-toric  C  C  cyls.  are  ground  with 
two  curves  on  convex  side  and  a  concave  curve  equal  to  the  cyl.  on 
the  opposite  side.  For  manufacturing  convenience,  all  concave  tone 
cylinders  are  transposed,  to  be  ground  on  plus  6  curves.  For  example : 
on  a  — .50  C  +6.00  +6.50  C  — 6.50. 

Example:  Plano-toric  C  C  cyl.  1.25:  +6.00  +7.25  3  —7-25. 

The  toric  compound.  Toric  compounds  in  the  majority  of  cases 
are  made  with  two  curves  on  the  outside,  and  any  desired  curve  on 
the  inside.  For  example :  +.25  on  a  .25  toric  compound :  +6.00  +6.25 
—5.75  equal  +.25  C  +.25. 


OPTICAL    LENSES  33 

Example :  +1.00  C  +-50  toric  compound :  +6.00  +6.50  C  — 5-oo 
equals  +1-00  +-50. 

Example:  +1.50  +75  toric  compound:  +6.00  +6.75  C  — ^4-50 
equals  +1.50  C  +.75. 

Example :  — 1.50  C  — -75  toric  compound :  +6.00  +6.75  C  — 8.25. 

Cement  Bifocals 

Cement  bifocals,  scales,  or  cement  wafers  are  made  by  three 
different  methods  and  are  generally  kept  in  stock  by  all  leading  jobbers. 
The  regular  segments  are  always  ground  +I-25  on  one  side,  with  any 
desired  curve  on  the  other  side,  and  wjll  fit  any  PCX  lens  that  may 
be  in  stock.  For  example,  if  you  want  to  add  -\-2.00  to  any  PCX 
lens,  the  segment  would  have  these  curves:  +1.25  +.75.  Should  you 
wish  to  add  +1.00,  then  you  would  have  +1.25  — .25. 

Should  you  wish  to  add  +3.00  you  would  have  +1.25  +1.75. 

Now  comes  the  piano  segment.  These  are  ground  piano  on  one 
side  and  any  curve  desired  on  the  opposite  side.  For  example :  +2.00 
segment  would  be:  +2.00  piano. 

Example:  +1.00  segment  would  be  +1.00  piano. 

Next  comes  the  toric  segment.  These  are  ground  +6-00  on  one 
side  and  any  desired  curve  on  the  other  and  will  fit  any  meniscus  C  X 
lens  in  stock.    For  example :  a  X^.oo  segment  would  be  +6.00  — 4.00. 

Example:  a  +1.00  segment  would  be  +6.00  — 5.00. 

Example:  a  +3.00  segment  would  be  +6.00  — 3.00. 

Cementing  Bifocals 

A  small  alcohol  lamp  is  commonly  used  and  would  be  practical 
for  the  beginner.  Secure  a  wooden  spring  clothespin,  which  is  used  to 
hold  the  lens  while  drawing  through  the  frame.  Use  a  clean,  soft 
cloth  with  wood  or  denatured  alcohol  to  clean  lens  and  segment.  With 
a  lens  measure  determine  which  side  of  the  segment  is  to  be  cemented 
on  the  lens.  The  hard  stick  cement  is  the  most  practical  for  quick, 
easy  cementing. 

Place  the  extreme  left  end  of  the  lens  in  the  clothespin  held  in 


34  OPTICAL    SHOP    PRACTICE 

the  left  hand,  with  the  lamp  directly  in  front  of  you.  Draw  the  lens 
back  and  forth  through  the  flame  slowly  about  ten  times.  Apply  the 
stick  cement  to  the  heated  lens,  which  will  melt  thei  cement,  leaving 
a  small  portion  on  the  lens.  Place  the  segment  carefully  on  the  melted 
cement.  Then  draw  the  lens  through  the  flame  until  the  cement  has 
spread  over  the  entire  area  under  the  segment.  Then  lay  the  lens  on 
a  pad  of  paper,  or  a  blotter,  and  with  a  match  or  lead  pencil  rubber, 
move  the  segment  from  side  to  side  until  all  air  bubbles  disappear. 
At  the  same  time  fix  the  position  of  the  segment  13/21  m/m  below 
the  center  of  the  lens  and  i;^,  m/m  toward  the  nasal  side.  Allow 
to  cool,  after  which  clean  cement  from  the  lens  and  edge  of  the  seg- 
ment with  a  tooth  brush  and  alcohol.  Then  edge  off  the  bottom  of 
the  segment. 

Quiz 

1 — How  are  stock  lenses  finished? 

2— In  what  focus  are  they  supplied? 

3— What  curves  has  a  P  C  X  1.00?  In  what  respect  does  a  P  C  C  lens 
differ  from  a  P  C  X? 

4— What  curves  has  a  P  C  C  1.25? 

5 — What  curve  is  always  on  a  meniscus  C  X?  What  curves  arc  on  a 
meniscus  C  X  1.00? 

6 — What  curve,  as  a  rule,  on  a  meniscus  C  C? 

7— How  many  curves  on  a  toric  C  X  cyl.  .50?    What  are  these  curves? 

8 — How  many  curves  are  on  one  side  of  a  toric  cyl.  C  C? 

9 — Draw  a  diagram  of  a  toric  C  C  2.00. 

10 — What  two  curves  are  on  one  side  of  a  toric  compound  ? 

11 — Make  a  diagram  of  a  toric  compound  +.25  sph.  C  +.25  cyl. 

12 — Make  a  diagram  of  a  toric  compound  +1.75  C  — .50  cyl. 

13 — Make  a  diagram  of  a  toric  compound  — 2.00  sph.  — .50  cyl. 

14 — What  curve  is  always  on  one  side  of  a  regular  segment?  What  kind 
of  a  lens  will  the  segment  fit? 

15 — What  curves  are  on  a  regular  segment,  +2.00? 

16 — What  curve  is  always  on  one  side  of  a  piano  segment? 

17 — What  curves  are  on  a  piano  segment,  +3.00? 

18 — Of  a  toric  segment? 

19 — What  kind  of  lens  will  this  segment  fit? 

20 — What  size  are  the  segments  made  originally? 


CENTERING    LENSES 


35 


CHAPTER  VI 

Centering  Lenses 

It  is  a  comparatively  simple  operation  to  center  a  lens  and  the 
same  can  be  learned  in  a  short  time.  Take  a  piece  of  heavy  white 
cardboard  lo  x  lo  inches,  and  through  the  center  of  this  draw  a  line 
from  top  to  bottom.  Then  draw  another  line  through  the  center  and 
at  right  angles  to  the  first.  This  cardboard  should  be  hung  on  the 
wall  at  a  convenient  height. 

Now,  stand  about  20  or  30  inches  away  from  this  cardboard,  take 
a  common  PCX  lens  in  the  left  hand  and  a  toothpick  "dotter"  in 

the  right  and  hold  the  lens  be- 
tween your  eye  and  the  card- 
board. It  is  best  to  use  but  one 
eye  in  this  work  without  closing 
the  other  eye  (when  one  eye  is 
closed  both  eyes  become  tired). 
Now  move  the  .  lens  backward 
and  forward  until  you  can  get 
a  good  view  of  the  intersecting 
lines  on  the  cardboard.  You 
will  note  that  when  you  move 
the  lens  upward  and  downward 
the  horizontal  line  will  appear 
broken,  and  that  when  you 
move  it  from  side  to  side  the  vertical  line  will  also  appear  broken. 

Move  the  lens  in  all  directions  until  the  lines  of  the  card  appear 
unbroken  and  then  dot  the  lens  at  the  point  where  they  intersect.  This 
will  be  the  correct  optical  center.  Repeat  this  practice  with  both  con- 
vex and  concave  lenses  and  you  will  be  astonished  how  quickly  the 
eye  becomes  trained  in  this  work. 


36  OPTICAL    SHOP    PRACTICE 

For  practical  purposes,  after  you  have  learned  the  principle  of 
centering  lenses,  it  is  advisable  to  adopt  some  standard  lens  centering 
instrument,  for  it  has  a  rest  for  your  hand  and  a  sliding  adjustment 
for  the  focus  of  the  lens,  so  as  to  keep  your  hand  in  a  steady  position. 
It  is  also  able  to  keep  your  sight  in  perfect  alignment  with  the  cross 
formed  by  the  intersecting  lines. 

Piano  cylinders  are  centered  in  exactly  the  same  way,  but  when 
you  turn  the  lens  slightly  you  will  note  that  the  line  will  have  a 
slanting  appearance.  Turn  the  lens  until  you  note  the  vertical  line 
appears  perfectly  straight,  then  put  a  dot  on  the  lines  at  the  top  and 
bottom,  and  this  will  be  the  true  cylindrical  optical  center,  or  center 
of  curvature. 

Compound  lenses  have  both  sphere  and  cylinder  combined,  and 
you  may  experience  a  little  trouble  in  finding  the  cyl.  Hold  the  lens 
as  before,  but  keep  turning  it  until  the  vertical  line  is  perfect,  then 
place  a  dot  at  the  top  and  bottom.  Now  move  the  lens  upward  and 
downward  until  the  lines  appear  unbroken  and  then  place  a  dot  in  the 
center.  The  top  and  bottom  dots  will  show  the  cylinder  center,  while 
all  three  dots  will  show  the  true  optical  center. 

For  convenience,  in  locating  the  axis  of  a  cylinder  the  use  of  a 
lens  measure  is  recommended.  You  will  notice  that  by  pressing  the 
lens  measure  against  the  cylinder  surface  of  the  lens  and  rotating  it, 
one  meridian  will  register  zero,  or  the  axis  of  the  cylinder,  and  the 
other  will  register  the  power  of  the  cylinder.  It  is  advisable  to  hold 
the  lens  with  the  axis  in  a  vertical  direction,  placing  the  dots  also  on 
the  vertical  meridian.  Do  not  turn  the  lens  so  far  that  you  lose  track 
of  the  cylinder  axis. 

In  centering  compound  lenses,  the  greatest  care  should  be  exer- 
cised so  as  to  get  the  right  side  of  the  lens  next  to  the  eye.    In  flat 
cylinders  and  compounds  this  will  be  found  rather  difficult,  therefore 
you  must  proceed  carefully.    The  use  of  the  lens  measure  is  the  best 
and  quickest  way  to  determine  the  greatest  convexity  or  concavity  of 


Genothalmic   Lens  Cutter 

The  only  Cutter  that  is  entirely  different 


The  new  Genothalmic  Lens  Cutter  is  distinctly 
the  very  latest  and  most  perfected  instrument  yet 
devised  for  cutting  lenses.  It  stands  out  above  all 
other  cutters  as  it  requires  absolutely  no  pads  or 
formers  of  any  kind  in  cutting  of  the  various  sizes 
and  shapes  of  lenses.  All  adjustments  are  made  on 
the  instrument  itself  by  merely  operating  two  ad- 
justing screws.  The  cut  is  absolutely  clean,  leaving 
an  edge  that  requires  practically  no  grinding  down 
to  edge. 

Any  size  eye  from  35  mm  to  70  mm  round  may 
be  cut  and  difiference  in  vertical  and  horizontal 
width  from  1  mm  to  18  mm,  as  small  an  oval  eye  as 
27x35,  may  be  had.  Drop  eyes  of  different  sizes 
can  be  cut  as  well.  After  short  experience  as  high 
as  one  hundred  to  one  hundred  and  twenty  lenses 
per  hour  have  been  cut. 

The  fine  mechanical  construction,  design  and 
finish  gives  you  in  the  new  Genothalmic  the  very 
best  that  can  be  had  in  a  lens  cutter.  Sold  by  your 
wholesaler. 

GENERAL  OPTICAL  COMPANY,  Inc. 


Manufacturers 
MT.  VERNON,  N.  Y. 


Sales    Offices 
Mount  Vernon 
Chicago 
San  Francisco 


Factories 
Mount  Vernon 
Toledo 
Tilton 


ID 


F.  A.  HARDY  S 


No.  1165.  "Toledo"  Opticians'  Pliers.  All  steel,  hand 
forged,  and  full  nickel  plated.  All  styles  of  jaws. 
Each n.65 

No.  1161.  Ordinary  quality  in  A.  B,  C  or  E  jaws,  nickel 
plated.      Small   than   No.    1165.      Each $1.00 


No.    114; 

Neutralizing 

Each $2.00 


This  hand: 
means  of  ke 
for  immedial 
Uttal  Plier  R 
table,  gives  t: 

This  is  mi 
pliers  and  c; 
hogany  finish 
No.  1149A.  F< 
No.  1149B.    F< 


No.    1179.      Protractor 
Each     $0.25 


No.   1115.     Peterson  Shanking  Plie 


The  Peterson  Shanking  Plier  is  used  for  changing 
the  shanks  on  frames  or  rimless  mountings  without 
removing  the  lenses.  It  is  made  to-  grasp  the  shank 
close  to  the  eye  wire  and  makes  a  neat  bend  near  the 
foot  of  the  bridge.  A  flat  nosed  plier  should  be  used 
in  connection  with  the  Peterson  Plier  in  making  this 
bend. 

The   Peterson   Plier  can  also  be  used  as  a   stud  plier 
for  offset   guard   eye  glasses  and   for  tilting  end   pieces 
of   frames. 
Each     $2.00 


bri 
us« 


NEW  YORK 


ATLANTA 


ST.  PAUL 


10  S.  WABASH  A 

DENVER  SAN   FRA 


J 


CO* —  specialties 


PTAL  PLIER  RACK 


cle  fills  a  long  felt  need  for  a 
adjusting  tools  in  order,  ready 
The  mere  appearance  of  the 
oniplete  with  tools  on  the  fitting 
jression  of  up-to-date  efficiency, 
two  sizes  for  holding  6  or  12 
supplied    in    either    oak    or    ma- 

iing   12  pliers.    Each $4.50 

ling      6   p'.iers.    Each 2.50 


Hardy    Shanking   Plier 


lier  is  used  for  changing  the  shanks  of 
when  lenses  have  been  removed.  It  is 
onnection  with  a  flat  nosed  plier.  Makes 
>end    close    to    the    foot    of    the    bridge. 


A    CHICAGO,  ILL. 

H  CO  DALLAS 


No.    1109.      Hardy   Strap   Plier 

This  plier  is  an  ideal  one  for  use  in  changing  the 
width  of  straps  for  mounting  either  flat  or  toric 
lenses.  A  sliding  bar  with  lugs  of  different  thick- 
nesses is  fitted  between  the  jaws.  Between  the  lugs  are 
slots  for  measuring  the  thickness  of  lenses.  In  using 
the  plier  the  lens  is  first  gauged  for  thickness,  then 
the  lug  of  the  desired  width  is  placed  between  the 
jaws.  The  strap  is  then  fitted  over  the  lug  and  the 
jaws  brought  together.  If  straps  are  to  be  altered 
for  toric  lenses  the  plier  is  held  at  a  slight  angle. 
This  plier  will  not  mar  the  straps. 
Each     $2.50 


Xo.    1107,       Hardy    Crest    Rolling    Plier. 
Patented   Feb.    16,    1915 

We  have  used  this  plier  in  our  shops  for  years  and 
do  not  hesitate  to  recommend  it  as  the  best  one  of 
its  kind.  With  it  one  can  roll  a  bridge  Avith  a  normal 
crest  (45  degrees)  to  35  degrees  more  vertical  or  15 
degrees  more  horizontal,  thus  obtaining  any  desired 
angle  from  15  to  80  degrees.  It  can  be  used  on  either 
M,  N  or  O  width  bridges  and  will  not  mar  the  bridge. 
Full   directions  supplied  upon  request. 


$1.25         Each 


$4.75 


SAN  ANTONIO 


WACO 


WICHITA  FALLS 


AUTOMATIC  LENS  SURFACING 
MACHINERY 


PLIERS 

For  Removing  and  Attaching  Shell  Rims 

H.  J.  STEAD  CO.,  Geneva,  N.  Y. 

New  York  City,  395-397  Broadway 


The  Professional  and  Trade  News 

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TME   OFTOlEraiie 


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CENTERING    LENSES  37 

any  lens.    Always  place  the  lens  with  the  weakest  convex  or  strongest 
concave  surface  toward  the  eyes,  excepting  in  the  case  of  bifocals. 

Get  a  protractor  card  (any  jobber  will  supply  one  on  request) 
graduated  in  five  degrees ;  dot  your  cylinder  lens  as  instructed  and  lay 
it  on  the  protractor  card.  If  you  wish  to  cut  it,  say,  axis  45,  turn  the 
lens  until  the  two  dots  come  to  45  on  the  card.  Now  make  a  series  of 
dots  across  the  line  on  the  180  line.  This  will  be  the  mechanical  axis, 
or  your  cutting  line.  Your  pattern  has  a  cross  line  on  it;  put  the 
long  line  on  the  pattern  over  the  long  line  on  the  lens,  hold  both 
pattern  and  lens  firmly,  and  proceed  to  cut. 

Flat  compounds,  also  toric  cylinders  and  compounds,  are  centered, 
dotted  and  marked  in  a  similar  manner.  It  will  be  well  to  practice  on 
several  kinds  before  you  attempt  to  cut  many,  as  that  will  give  you 
ample  time  for  careful  study  of  the  process  of  marking. 

In  de-centering  any  kind  of  lens,  it  is  done  by  simply  moving 
the  pattern  up  or  down,  in  or  out,  and  then  cutting  the  lens  as  previ- 
ously instructed.  If  you  want  greater  de-centration,  it  is  well  to 
reduce  your  lens  to  a  prism  and  have  your  jobbing  house  grind  it  for 
you. 

For  automatic  machine  work,  the  lens  should  be  cut  two  milli- 
meters larger  than  the  actual  size  wanted.  For  hand  edging  one 
millimeter  will  be  sufficient. 


Quiz 

1 — What  colored  cardboard  is  used  for  centering?    What  size? 
2 — How  do  you  make  the  lines  on  the  card? 

3 — In  order  to  use  the  card  what  do  you  do?    How  far  from  the  eye? 
4 — In  what  hand  do  you  hold  the  lens?     In  what  direction  do  you  move 
the  lens?    At  this  point  what  are  you  looking  to  find? 
5 — What  do  you  use  as  a  dotter?  \ 

6 — When  do  you  stop  moving  the  lens? 
7 — What  is  this  point  called? 
8 — In  centering  a  lens  do  you  use  both  eyes? 


38  OPTICAL    SHOP    PRACTICE 

9 — What  is  done  to  center  piano-cylinders? 
10 — What  instrument  is  used  in  finding  the  cyl.  side? 
11 — How  will  the  vertical  line  appear? 
12 — Where  do  you  put  the  dots  on  cylinder  lens  ? 
13 — Why  should  care  be  used  in  marking  the  cyls.  and  compounds  ? 
14 — What  kind  of  card  is  used? 
15 — How  is  it  graduated? 
16 — How  is  the  lens  to  be  turned? 
17 — How  many  dots  should  be  made  across  the  lens? 
18 — How  do  you  put  the  pattern  on  the  lens? 
19 — How  do  you  de-center  a  lens? 

20 — What  size  should  cut  be  made  for  automatic  grinding?    What  size  for 
hand  grinding? 


FOR  YOUR  PRACTICE 


Rx 

0.  D.  Practice  100%  )    _    lUE    iFTOilET^D© 


0.  S.  Theory    100%  \  WEE 


[  = 


SURFACING 


CHAPTER  VII 

Surfacing 

To  be  a  successful  surface  grinder  the  operator  must  possess  a 
certain  amount  of  natural  mechanical  ability  in  addition  to  giving 
his  work  deep  study,  for  it  requires  both  to  master  the  principles  of 
this,  and  much  more  time  and  practice  are  necessary  than  in  the 
operations  thus  far  dealt  with. 

There  are  different  kinds  of  surfacing  machines  in  use,  but  it 
is  all  a  matter  of  personal  preference  for  the  reason  that  all  are  con- 
structed along  the  same  lines,  involving  the  same  principle.  It  is  all 
up  to  the  individual,  depending  upon  his  power  to  grasp  necessary 
details  and  then  carry  out  their  requirements.  It  is  no  "kid  glove" 
work,  and  the  person  who  is  afraid  of  getting  a  little  dirt  on  his  hands 
had  better  not  undertake  to  do  surfacing.  Furthermore  he  must 
make  up  his  mind  to  wear  overalls,  unless  he  has  a  suit  to  spoil  every 
day. 

A  person  of  a  mechanical  turn  of  mind  is  much  more  likely  to 
become  an  efficient  surface  grinder,  as  such  an  individual  will  without 
any  doubt  make  a  greater  success  of  his  efforts  than  the  one  who 
merely  follows  routine  without  a  constant  desire  to  know  the  whys 
and  wherefores,  with  an  eye  open  to  improve  upon  his  work.  These 
factors  should  be  carefully  weighed,  for  an  incompetent  surface 
grinder  will  prove  a  liability  to  himself  instead  of  an  asset. 

As  usual,  common  glass  should  be  used  first  (extra  thick  window 
glass  will  be  good  to  use),  which  should  be  cut  into  squares  or  circles, 
as  desired.  The  first  thing  to  learn  is  how  to  cement  the  glass  to  the 
iron  holders  which  come  with  the  machines.  There  are  several  kinds 
of  these  holders,  or  blocks,  some  being  flat,  while  others  are  concave 
or  convex. 


40  OPTICAL    SHOP    PRACTICE 

Blocking  Lenses 

A  good  cement  for  blocking  lenses  is  made  from  common  resin 
and  black  tar,  in  the  proportion  of  eight  parts  of  resin  to  two  parts  of 
tar,  or  in  other  words,  in  the  ratio  of  80%  to  20%.  Boil  these  in- 
gredients together  until  they  are  a  very  thin  liquid,  then  strain  the 
liquid  through  cheese  cloth  and  pour  into  small  cardboard  boxes,  to 
cool.  This  straining  is  important,  for  small  particles  of  foreign 
matter  are  in  the  resin  and  tar  and  must  be  strained  out,  as  if  permitted 
to  remain  they  may  scratch  the  lens.  You  can  also  purchase  this 
cement  from  jobbing  houses,  which  always  carry  it  in  stock.  Unless 
you  intend  to  do  a  great  deal  of  surfacing  work  it  would  not  pay  to 
undertake  to  make  your  own  cement. 

The  next  thing  to  do  is  to  get  the  lens  (or  glass)  on  the  block. 
Heat  the  block  slightly  (not  real  hot)  and  then  run  some  of  the  cement 
upon  it  in  just  the  same  way  that  you  probably  have  often  seen  sealing 
wax  applied  to  a  package  in  an  express  office.  For  this  purpose  use  a 
common  gas  flame. 

After  the  block  has  been  warmed,  next  do  this  same  thing  to  the 
lens,  taking  care  to  warm  the  latter  in  such  a  way  that  the  heat  will 
not  be  applied  more  to  one  part  than  to  another,  as  this  would  in  all 
likelihood  tend  to  crack  it.  Then  run  a  small  amount  of  the  cement 
on  the  lens  as  you  did  on  the  block.  Next  run  the  blaze  over  the 
cement  on  the  block  and  apply  the  side  of  the  lens  having  the  cement 
on  it  to  the  block,  being  careful  to  center  the  lens  on  the  block — that 
is  to  have  the  center  of  the  lens  directly  upon  the  center  of  the  block. 
You  should  practice  this  operation  many  times,  so  as  to  acquire  the 
"trick,"  when  you  can  do  it  quickly  and  accurately,  always  using  com- 
mon glass  before  you  attempt  to  use  a  good  lens. 

It  is  always  a  good  idea  to  have  the  bench,  or  table,  upon  which 
you  work  covered  with  tin  or  sheet  iron,  so  that  any  cement  that  may 
run  off  the  lens  or  block  may  be  saved  and  used  again.  It  is  also  a 
very  good  idea  to  keep  the  blocking  bench,  or  table,  away  from  the 
cold  or  a  draft,  in  order  to  prevent  breakage. 


SURFACING  41 

Just  as  in  many  other  lines  of  work,  you  may  find  no  two  people 
who  block  lenses  in  the  same  manner,  even  though  they  are  exj>erts, 
but  the  principles  are  invariably  the  same.  You  will  find,  after  you 
have  been  at  it  for  some  time,  that  you  will  develop  a  way  of  your 
own  that  comes  most  easily  to  you,  and  if  you  stick  right  at  it  and  pay 
close  attention  to  the  directions  as  outlined  thus  far  you  will  be  able 
in  a  reasonably  short  time  to  block  a  lens  in  about  one  minute. 

When  you  have  a  flat  surface  to  block  use  a  flat  block. 

When  you  have  a  convex  surface  to  block  use  a  concave  block. 

When  you  have  a  concave  surface  to  block  use  a  convex  block. 

It  is  always  well  to  get  a  good  layer  of  cement  between  the  lens 
and  the  iron  block,  because  should  the  glass  get  too  close  to  the  iron 
it  is  more  likely  to  break.  About  ^  of  an  inch  of  cement  between 
glass  and  block  is  safe.  This  operation  of  blocking  is  one  of  the  most 
important  of  all  those  involved  in  the  working  up  of  a  lens — it  is 
vital.  In  blocking  a  cylindrical  lens,  draw  a  white  line  (white  ink) 
showing  the  axis  of  the  lens.  Upon  proper  blocking  depends  your 
success  in  grinding.  It  is  a  safe  statement  that  thousands  of  lenses 
are  broken  every  week  in  this  country  through  inefficient  blocking, 
thus  involving  a  large  loss  in  money,  time  and  labor. 

Surfacing  Machines 

Practically  the  same  principle  is  involved  in  the  construction  of 
all  the  surfacing  machines  in  use.  They  are  all  the  result  of  experi- 
ence and  careful  study,  and  their  operation  depends  upon  the  indi- 
vidual handling  them  and  the  kind  of  work  to  be  done.  Carelessness 
on  the  part  of  the  operator  will  prevent  the  finest  machine  on  the 
market  from  turning  out  good  work.  Intelligence  must  be  exercised 
at  all  times  and  the  machine  must  be  kept  clean.  Indifference  on  the 
part  of  the  worker  and  lack  of  cleanliness  as  regards  his  care  of  the 
machine  will  only  mean  trouble,  and  that  very  soon,  too.  Many  a 
machine  has  been  given  the  blame  that  should  be  placed  upon  its 
operator. 


42  ^  OPTICAL    SHOP    PRACTICE 

It  has  been  shown  by  experience  that  about  650  revolutions  per 
minute  is  the  right  speed  at  which  to  run  the  machine,  for  this  is 
fast  enough  for  all  kinds  of  work.  If  the  machine  is  run  at  a  greater 
speed  this  will  only  result  in  throwing  off  the  emery  too  rapidly,  be- 
sides which  it  will  have  a  tendency  to  overheat  the  lens.  It  will  be 
found  that  one-half  horse  power  is  sufficient  for  each  spindle.  Always 
see  to  it  that  the  machine  is  kept  free  from  emery  dust,  for  if  this 
gets  into  the  bearings  it  will  cut  the  same  and  ruin  the  machine. 

A  surfacing  machine  is  usually  equipped  with  an  upright  spindle, 
with  a  taper  on  the  top  of  the  spindle,  to  hold  the  tool.  It  is  also 
equipped  with  a  handle  across  the  machine  provided  with  an  adjustable 
pin,  to  hold  the  block.  This  handle  is  also  made  adjustable  so  that 
it  can  give  the  pin  the  proper  pitch,  or  angle.  Nearly  all  machines  are 
fitted  with  foot  pedals,  for  starting  and  stopping,  and  some  also  are 
equipped  with  an  automatic  attachment  for  polishing.  Great  care 
and  persistence  in  practice  should  be  exercised  and  the  operator  should 
become  a  good  grinder  before  undertaking  any  automatic  work,  when 
it  comes  to  the  question  of  handling  spherical  lenses. 

The  tools,  or  laps,  that  you  will  require  for  spherical  work  are 
made  from  special  iron,  the  low  power,  or  flat  laps,  being  about  4>^ 
inches  wide.  As  curves  are  shorter  in  radius,  the  diameter  will  be 
much  less.  Caution — Before  removing  lap  from  the  spherical  spindle, 
always  allow  the  maMne  to  conie  to  a  full  stop.  Otherwise  a  bad  cut 
or  injury  to  your  hand  may  result. 

The  surface  grinder  must  give  prop>er  care  to  his  laps,  for  the 
accuracy  of  his  lens  depends  upon  their  accuracy.  In  the  process  of 
grinding,  the  laps  will  become  worn  and  eventually  incorrect  in  con- 
tour. An  expert  will  endeavor  to  maintain  a  uniform  wear  on  the  lap 
and  will  frequently  test  its  curvature  by  means  of  a  metal  gauge.  It  is 
therefore  necessary  to  have  a  metal  gauge  for  every  lap  curvature. 
When  laps  become  noticeably  out  of  true,  they  may  be  retrued  by  use 
of  a  carborundum  stick,  such  as  is  used  in  truing  edging  stones,  held 
against  the  lap  either  by  hand  or  while  the  lap  is  rotating  on  the  regular 


SURFACING  43 

Spindle  at  high  speed.  The  retruing  of  cyUnder  laps  is  much  more 
difficult  and  it  may  become  necessary  to  return  the  laps  to  the  factory 
occasionally  to  be  retrued  to  perfect  curvature. 

When  testing  a  lap  by  means  of  a  gauge,  the  lap  should  be  removed 
from  the  spindle  and  held  toward  a  light,  with  the  gauge  held  square 
with  the  lap  surface.  Never  try  to  gauge  a  lap  while  on  the  spindle, 
especially  if  in  motion,  as  this  will  ruin  the  accuracy  of  the  gauge. 
Likewise,  never  remove  the  lap  or  put  it  on  while  there  is  rotation 
in  the  spindle,  as  this  will  cause  wear  in  the  lap  socket  or  spindle  taper, 
this  causing  the  lap  to  set  loosely  on  the  spindle.  If  you  have  done 
this,  do  not  blame  the  manufacturer  if  new  laps  fail  properly  to  fit  the 
spindles. 

Quiz 

1 — What  is  the  first  step  in  surfacing? 

2 — What  is  a  block?    Are  they  all  of  one  kind?    Describe. 

3 — What  is  a  good  cement  for  blocking  lenses?    Describe  how  prepared. 

4 — How  do  you  apply  the  cement? 

5 — Describe  the  preparation  of  the  lens  for  blocking. 

6 — When  you  have  a  flat  surface  to  block  what  kind  of  block  do  you  use?>. 
A  concave  surface;  a  convex  surface? 

7 — What  is  the  best  thickness  of  cement  to  employ? 

8 — What  is  about  the  right  speed  for  a  surfacing  machine?    What  happens 
if  it  is  run  too  fast  ?    What  is  about  the  proper  power  for  each  spindle  ? 

9 — How  is  a  surfacing  machine  usually  equipped?    Go  into  details. 

10 — Describe  the  tools,  or  laps,  used  in  spherical  work. 


44  OPTICAL    SHOP    PRACTICE 


CHAPTER  VIII 

Roughing  Lenses 

This  brings  us  to  the  matter  of  grinding  material  that  will  be 
found  necessary  in  lens  surfacing.  Different  experts  have  their  own 
choice  in  this.  Their  preference  lies  between  emery,  alundum  and 
carborundum,  No.  60  or  70  of  either  being  best  for  use.  It  is  more 
than  likely  that  most  of  them  use  No.  70. 

The  grinding  material  is  put  into  the  mixing  pan  and  enough 
water  is  added  to  make  it  wet,  after  which  it  is  dipped  up  and  applied 
to  the  tool  with  a  small  flat  stick,  or  paddle,  or  the  hand.  After  you 
have  selected  the  proper  tool  for  the  job  that  you  are  about  to  turn 
out,  a  little  of  the  mixture  is  applied  and  then  the  lens  is  placed  on 
the  tool.  Now  adjust  the  pin  in  the  handle  to  approximately  a  right 
angle  with  the  curvature  of  the  tool,  when  the  point  rests  about  mid- 
way between  the  edge  and  center  of  the  tool.  Next  adjust  the  pin  in 
the  iron  block  and  turn  on  the  power.  The  two  opposite  sides  of  a 
cylindrical  lens  measured  on  the  axis,  or  white  line,  should  be  equal 
in  thickness,  to  avoid  prismatic  results,  and  the  two  points  at  right 
angles  to  the  axis  should  also  match  each  other  in  thickness,  but  will 
not  be  the  same  thickness  as  the  former  calipration. 

Keep  dipping  up  the  mixture  and  putting  it  on  the  tool  meanwhile, 
by  means  of  the  hand,  moving  the  lens  backward  and  forward  from 
the  center  to  the  outside  of  the  tool  farthest  from  you.  At  the  start 
do  not  apply  much  pressure,  as  you  will  soon  get  the  grinding  sound 
and  will  quickly  learn  the  proper  amount  of  pressure  and  the  right 
quantity  of  the  emery  to  apply. 

It  is  best  to  practice  on  ten  or  fifteen  lenses  before  taking  the 
next  step.  For  example,  if  you  want  to  grind  a  +3.00  spherical  lens, 
i}4  millimeter  thick,  you  should  first  rough  it  down  to  about  i>^ 
millimeters  with  rough  emery.    This  "roughing  out,"  as  it  is  called,  is 


ROUGHING    LENSES  45 

the  first  step  in  surfacing  and  is  one  in  which  you  should  become 
perfect  before  attempting  to  go  farther. 

Learn  the  "good  cutting  sound,"  learn  to  be  economical  with  the 
grinding  mixture,  learn  to  dip  up  the  mixture  properly,  and  above  all 
learn  to  "rough  out"  lenses  to  the  proper  thickness.  If  you  make  up 
your  mind  to  do  this  and  stick  at  it  until  you  accomplish  it  you  will 
save  a  great  deal  of  time  when  you  have  to  grind  a  large  number  of 
spherical  lenses,  and  by  giving  close  attention  to  the  small  operations 
explained  here  you  will  be  sure  to  master  the  first  and  one  of  the  most 
important  steps  in  surface  grinding. 

After  you  have  made  yourself  proficient  in  roughout  work,  the 
next  thing  is  to  take  up  finer  work,  in  which  the  grinding  mixture  is 
No.  120  or  150  of  the  emer}%  alundum  or  carborundum.  Many  ex- 
perts prefer  the  No.  120,  as  it  seems  to  produce  the  best  results.  This 
is  placed  in  a  porcelain  bowl,  crock  or  enameled  cup  (never  use  a  tin 
cup),  and  sufficient  water  is  ?,dded  to  make  it  wet  before  it  is  applied  to 
the  tool.  A  great  many  good  grinders  prefer  a  brush  tO'  a  stick  or 
paddle  in  applying  this,  experience  having  demonstrated  that  the 
brush  enables  the  operator  to  apply  the  mixture  more  evenly  and 
economically. 

In  this  part  of  the  work  do  not  grind  the  lens  down  too  far.  It 
takes,  as  a  rule,  two  or  three  minutes  to  take  out  the  rough  emery 
"pits,"  upon  finishing  which  you  will  notice  that  the  surface  has  be- 
come smoother  and  the  lens  a  little  thinner.  You  will  also  note  that 
there  is  a  different  grinding  sound.  It  is  important  to  watch  the 
thickness  of  the  lens  in  this  part  of  the  work.  By  doing  so  you  will 
soon  learn  just  how  much  time  is  necessary  in  each  operation  and 
you  will  learn  the  proper  amount  of  pressure  to  exert  on  the  handle. 

Never  guess  at  the  time,  at  least  for  some  period  after  you  have 
started  on  this  part  of  the  work.  Use  a  clock  or  watch  for  at  least  a 
few  days,  and  you  will  find  that  experience  will  enable  you  to  know 
the  proper  length  of  time  to  within  probably  a  few  seconds. 

The  thickness  is  another  thing  in  connection  with  which  guess- 
work should  never  be  used.     Get  a  pair  of  calipers  and  during  your 


46  OPTICAL    SHOP    PRACTICE 

practice  period  measure  the  thickness  of  the  lens  frequently.  Your 
eye  will  in  time  become  so  trained  that  you  will  be  able  to  discern  the 
thickness  required  for  the  different  lenses,  and  this  will  mean  a  big 
saving  in  time.  Practice  on  all  the  lenses  that  you  have  roughed  out, 
making  some  thin,  some  medium  thick  and  others  fairly  thick. 

The  right  kind  of  emery,  alundum  or  carborundum  for  your 
grinding  mixture  in  the  next  step  is  No.  2  F.*  This  is  prepared  in  a 
bowl  or  crock,  as  the  other  (No.  120)  is  prepared,  and  apply  it  with  a 
brush.  In  examining  the  lens,  you  will  notice  that  it  is  becoming  still 
more  smooth,  and  you  should  every  now  and  then  wipe  off  the  work 
and  look  for  scratches  that  will  sometimes  appear.  If  you  find  any 
scratches,  re-grind  the  lens  until  the  same  are  removed.  Don't  forget 
to  wash  and  dry  off  the  work  occasionally. 

Always  keep  plenty  of  the  grinding  mixture  on  the  tool,  and 
never  let  the  mixture  become  dry,  as  this  will  have  a  tendency  to  pro- 
duce scratches  or  chip  and  put  deep  holes,  or  pits,  in  the  lens. 

Bear  these  things  in  mind:  Keep  your  eye  on  the  lens;  don't  use 
too  much  pressure ;  keep  the  handle  and  pin  clean. 

You  are  now  ready  for  the  last,  and  most  important  step — that 
of  using  the  "finishing  emery,"  or  mixture,  which  is  not  only  very  fine 
but  also  expensive  and  should  always  be  kept  in  a  dry  place  and  pro- 
tected from  foreign  matter.  It  is  safest  to  keep  it  in  a:  place  by  itself, 
away  from  the  other  emeries  and  carefully  covered,  for  any  foreign 
matter  in  it  might  produce  a  scratch,  which  is  the  very  thing  that 
must  be  avoided  in  the  finishing  of  the  lens. 

In  using  the  last  emery  you  will  note  that  there  is  no  grinding 
sound.  This  is  because  of  the  great  fineness  of  the  emery.  Do  not  let 
the  tool  get  dry,  and  do  not  use  too  much  pressure.  Watch  the  lens 
all  the  time  while  you  are  grinding,  and  after  you  have  been  working 
on  it  for  three  or  four  minutes  take  the  lens  off,  wash  it,  then  dry 
with  a  clean  rag  and  hold  it  up  to  the  light  and  look  carefully  for  pits 
and  scratches.  Also  note  the  degree  of  smoothness  it  has  received. 
It  is  a  good  idea  to  use  a  magnifying  glass  in  looking  for  scratches. 


ROUGHING    LENSES  47 

Too  much  importance  cannot  be  laid  upon  this  last  operation 
with  the  emery,  and  the  operator  must  be  sure  that  every  imperfection 
has  been  removed  from  the  surface  before  going  one  step  farther. 
Care  must  be  taken  that  no  rough  emery  is  on  the  hands,  or  even  the 
clothing,  for  this  may  find  its  way  to  the  lens,  which  will  mean  a 
scratch  or  perhaps  several  scratches.  Very  often  a  worker  who  has 
been  careless  in  this  respect  has  blamed  the  mishap  on  the  emery.  To 
make  sure  that  you  will  produce  the  desired  results,  see  that  the  block 
and  lens  are  clean,  perfectly  clean.  Keep  the  edg^  of  the  lens  clean. 
If  you  observe  these  precautions,  together  with  keeping  the  machine 
perfectly  clean,  you  will  avoid  the  troubles  which  have  proven  so 
exasperating  to  many  lens  grinders.  Scratches  and  pits  are  the  real 
"bugbear"  of  this  work. 

Polishing 

After  a  lens  is  properly  ground,  the  next  step  is  polishing.  This 
is  naturally  a  delicate  operation,  requiring  care  and  the  finest  material. 
The  best  grade  of  finely  powdered  red  rouge  is  used,  and  this  can 
be  obtained  at  any  optical  supply  house.  It  comes  in  five-pound  cans, 
ready  for  use. 

A  polishing  cloth  is  used  for  this  last  operation,  and  these  cloths, 
which  are  specially  treated,  are  sold  by  optical  jobbers  and  are  perfect 
for  the  work.  As  in  most  other  articles  used  in  connection  with  lens 
work,  these  cloths  come  in  several  varieties,  and  you  will  very  likely 
develop  a  preference  for  a  certain  kind  and  will  use  the  kind  which 
best  suits  you  in  all  of  your  future  surface  work. 

Various  methods  are  employed  in  fastening  the  polishing  cloths 
to  the  tool.  In  some  cases  the  grinder  cements  the  cloth  to  the  tool 
by  heating  the  latter  and  then  applying  blocking  cement,  laying  the 
cloth  on  this  smoothly  and  letting  the  tool  become  cool,  after  which 
it  will  be  found  that  the  cloth  will  adhere  firmly.  Care  must  be  taken 
to  press  the  cloth  down  upon  the  tool,  so  that  it  will  assume  the  exact 
curvature  of  the  same.     Some  grinders  use  a  cloth  about  a  half  inch 


48  OPTICAL    SHOP    PRACTICE 

smaller  than  the  tool,  while  others  prefer  one  larger.  It  will  not  take 
long  for  you  to  decide  which  you  prefer.  Some  grinders  use  a  special 
set  of  laps  for  polishing,  cut  with  radius  greater  or  less  by  the  thick- 
ness of  felt,  so  that  laps  with  felt  added  will  have  correct  radius.  This 
will  shorten  time  in  polishing. 

Another  method  of  fastening  the  cloth  to  the  tool  is  by  using  a 
cement  made  of  powdered  resin,  tar  and  benzine.  This  is  prepared 
by  using  about  half  a  pound  of  the  resin,  to  which  about  one  ounce  of 
tar  is  added,  and  then  a  little  benzine  is  poured  on  this  mixture.  Set 
it  aside  for  two  days  or  so,  and  you  will  find  that  the  mass  has  assumed 
a  glue  which  can  be  applied  to  the  tool  with  a  stick  while  the  latter  is 
in  motion,  after  which  the  cloth  is  pressed  down  firmly  to  fit  the  curv- 
ature of  the  tool,  upon  which  it  is  ready  for  the  polishing  process.  As 
most  jobbers  sell  practically  this  same  kind  of  glue,  it  is  advisable  to 
buy  it  from  them  and  avoid  the  trouble  of  making  it  yourself. 

The  rouge  is  prepared  by  placing  it  in  a  porcelain  or  enameled 
vessel,  then  adding  water  until  it  is  the  consistence  of  a  thick  paste, 
after  which  it  is  applied  to  the  cloth  in  the  same  manner  as  that  in 
which  the  emery  mixture  is  applied,  whereupon  the  polishing  may  be 
started.  One  thing  for  which  to  watch  is  when  the  work  begins  to 
emit  steam.  This  is  caused  by  the  heat  generated  in  the  polishing 
process,  and  the  machine  should  be  stopped  for  a  time,  in  order  to  let 
the  lens  cool. 

While  the  polishing  process  is  not  necessarily  a  very  slow  one,  at 
the  same  time  it  should  not  be  hurried,  and  too  much  pressure  should 
not  be  applied.  It  usually  takes  from  five  to  seven  minutes  to  obtain 
a  polish,  even  after  the  worker  has  become  an  expert,  and  the  be- 
ginner will  find  that  it  takes  longer  than  this,  for  there  is  a  little 
"trick"  in  applying  the  rouge  which  comes  only  with  experience,  be- 
sides learning  just  how  much  pressure  will  produce  the  most  satisfac- 
tory results.    However,  mastery  of  these  details  will  come  in  time. 

As  you  go  on  with  the  polishing  you  will  notice  that  the  lens  has 
a  tendency  to  ''pull."  This  is  caused  by  friction.  Sometimes  two  or 
three  lenses  will  jump  off  the  block,  and  this  is  caused,  as  a  rule,  by 


ROUGHING    LENSES  49 

not  having  the  pin  set  at  the  proper  angle,  while  again  it  might  be  the 
result  of  pressing  too  hard  on  the  handle.  These  mishaps  are  only 
the  result  of  inexperience  and  in  time  will  become  very  rare  with 
you,  as  you  become  more  familiar  with  the  work.  Just  don't  "lose 
your  head,"  but  keep  right  at  it,  realizing  that  others  who  are  now  ex- 
perts had  the  same  troubles  to  overcome  and  that  they,  too,  had  to 
take  their  time. 

Surfacing  Rough  Cylinders 

You  are  now  brought  to  the  first  actual  work  on  a  lens,  going 
on  the  assumption  that  you  have  thoroughly  familiarized  yourself  with 
the  various  details  and  operations  described  thus  far  as  a  result  of 
plenty  of  practice.    We  shall  take  the  following  combination: 

-{-.2^  sph,  +  .^5  cyl.  Hat  compound,  about  lYi  millimeters  thick. 

Flat,  rough  cylinders — that  is  flat  lenses  with  the  cylinders 
finished  on  one  side  and  the  other  side  rough — can  be  obtained  from 
optical  jobbers  in  a  great  variety  of  thickness.  They  come  in  in- 
dividual containers,  with  the  focus  and  thickness  plainly  marked  on 
them,  usually  2,  4,  6,  or  8  millimeters  thick  and  47  millimeters  square. 

To  grind  the  combination  specified,  pick  out  the  thinnest  rough 
cylinder  that  you  can  find,  3^  millimeters  is  thick  enough.  Always 
hold  it  up  to  the  light  first  and  examine  it  carefully,  to  make  sure  that 
it  is  free  from  all  imperfections,  such  as  bubbles  or  deep  scratches 
on  the  finished  side.  Never  forget  to  use  a  lens  measure,  or  gauge, 
and  measure  the  lens  before  starting  to  block  it  on  the  iron  block. 

It  is  a  very  good  idea  to  draw  a  line  through  the  axis.  This  can 
be  done  with  a  toothpick  dipped  in  white  ink,  or  a  liquid  made  from 
chalk  and  water.  This  line  should  be  drawn  on  the  cylinder  side. 
After  you  have  done  this  and  are  sure  that  there  are  not  any  imper- 
fections you  can  proceed  to  block  the  lens  as  you  have  already  been 
instructed. 

Now,  make  note  of  the  fact  that  the  lens  is  3J^  millimeters  in 


50  OPTICAL    SHOP    PRACTICE 

thickness,  and  your  object  is  to  finish  it  i>4  millimeters  thick,  there- 
fore it  will  require  very  little  of  the  No.  70  emery  to  rough  grind  it. 
Be  careful  not  to  grind  the  lens  too  thin  with  the  first  grinding  mix- 
ture. Leave  some  of  it  for  the  finer  grinding  mixture  to  take  off. 
Always  measure  the  thickness  from  side  to  side  and  from  end  to  end, 
at  right  angles  to  each  other. 

The  lens  will  often  be  found  thicker  at  one  side  than  at  the  other, 
which  shows  that  it  is  out  of  center.  If  you  find  it  to  be  this  way  it 
is  useless  for  your  purpose. 

Always  make  it  a  point  to  make  sure  that  a  lens  is  properly 
centered  after  it  has  been  roughed  out.  If  it  is  not  properly  centered 
you  must  grind  down  the  thick  side  to  the  exact  thickness  of  the  other. 
The  correct  way  to  do  this  is  to  hold  the  lens  in  the  left  hand  and 
put  it  on  the  tool  while  the  latter  is  revolving,  pressing  slightly  on 
the  thicker  side.  This  will  take  off  the  "prism"  and  you  can  then 
pioceed  to  use  the  handle  and  pin  and  finish  surfacing  the  lens.  Never 
use  the  handle  and  pin  when  centering  a  lens, 

A  good  way  to  "get  your  hand  in"  is  to  take  a  piece  of  old  glass 
and  grind  it  prismatic — ^that  is  with  one  side  thicker  than  the  other — 
and  then  center  it  again.  This  will  teach  you  the  necessary  amount 
of  pressure  to  use  as  well  as  at  what  angle  to  hold  the  lens. 

The  combination  that  you  are  supposed  to  be  working —  +.25 
sph.  +.25  cyl.  flat  compound,  i>4i  millimeters  thick — requires  very 
little  grinding,  and  an  expert  grinder  would  finish  a  pair  of  such  in 
20  or  30  minutes. 

For  the  next  combination,  try  a  stronger  lens,  say  a  +6.00  sph. 
+  1.00  cyl.  flat  compound,  y^  millimeter  thick  at  the  edge. 

This  being  a  much  stronger  lens,  it  will  be  necessary  to  pick  out 
a  thicker  rough  cylinder,  say  about  4  or  5  millimeters  thick.  Proceed 
as  before,  examining  carefully  for  imperfections,  and  marking  the 
axis  line  in  white  ink.  After  you  have  ground  this  lens  for  2  or  3 
minutes,  you  will  note  that  the  full  curve  is  not  ground  on.    Continue 


ROUGHING    LENSES  51 

grinding  with  the  No.  70  until  the  lens  is  about  one  millimeter  thick. 
Make  sure  that  it  is  properly  centered  and  then  proceed  with  the 
other  grades  of  emery  as  instructed. 

When  you  polish  this  lens  you  will  note  the  greater  tendency  it 
will  have  to  "pull/'  or  jump,  which  you  will  probably  find  is  caused 
by  the  cloth's  being  too  thick.  You  will  also  notice  that  the  edge 
of  the  lens  polishes  more  rapidly  than  the  center,  which  will  remain 
a  dull  grey.  This  can  be  overcome  by  using  a  smaller  piece  of  cloth, 
or  you  can  use  a  thick  cloth  with  a  tool  a  quarter  diopter  weaker  than 
would  otherwise  be  selected.  Now,  after  you  have  substituted  the 
smaller  piece  of  cloth  you  will  find  that  the  center  polishes  more 
rapidly  than  the  edge,  the  latter  now  assuming  the  dull,  grey  appear- 
ance. Practice  with  a  number  of  lenses  will  soon  enable  you  to  de- 
termine the  proper  thickness  of  cloth  and  also  the  right  amount  of 
pressure  to  exert  on  the  handle.  Experience  has  demonstrated  that 
by  following  this  method  the  amount  of  breakage  is  greatly  reduced. 

Now  let  us  proceed  to  the  next  combination,  say  a  — ^4.00  sph. 
— .50  flat  compound,  about  >^  millimeter  in  the  center. 

Pick  out  a  rough  cylinder,  3  or  4  millimeters  thick,  make  the 
examination  for  imperfections,  draw  the  white  axis  line  and  block  it. 
Watch  the  lens  closely  and  you  will  note  that  you  are  grinding  its 
center  first.  Be  careful  in  this  operation,  for  if  you  are  not  cautious 
you  will  grind  right  through  the  lens  onto  the  iron  block.  The  lens 
should  be  taken  oflf  frequently  and  the  thickness  ascertained,  and  you 
can  do  the  latter  by  holding  it  up  to  the  light.  Another  important 
point  is  to  leave  some  of  the  work  for  the  finer  emery  to  do. 

Right  here  we  would  suggest  as  a  good  idea  that  you  block  up 
several  pieces  of  thick  window  glass,  and  on  these  grind  different 
minus  curves.  This  will  train  your  eye  to  note  the  proper  thickness 
of  the  centers  and  edges,  and  it  will  not  be  very  long  before  you  will 
have  mastered  the  art  of  grinding  concave  lenses  to  the  proper  thick- 
ness in  the  center.  Never  lose  sight  of  the- fact  that  you  must  con- 
stantly watch  the  thickness  of  the  lens  on  all  edges,  so  as  to  avoid  their 


52  OPTICAL    SHOP    PRACTICE 

becoming  prismatic.   Observe  this  carefully  and  always  begin  to  center 
up  the  lens  before  it  gets  too  thin  in  the  center. 

All  of  the  flat  combinations — that  is  plus  on  plus ;  minus  on  minus ; 
plus  on  minus  and  minus  on  plus — are  ground  by  the  same  method. 
The  really  important  thing  to  bear  in  mind  is  to  get  both  sides  the 
same  thickness  and  both  ends  the  same  thickness.  Always  use  a  flat 
iron  block  for  the  flat  lenses,  and  when  you  grind  a  weak  curve,  say  a 
+.25,  see  that  the  pin  in  the  handle  is  straight  up  and  down,  or  j>er- 
pendicular.  If  you  have  a  plus  6.00  curve  to  grind,  slant  the  pin 
slightly  forward,  and  if  you  wish  to  grind  a  minus  6.00  curve  slant  the 
pin  slightly  backward,  as  previously  explained.  This  is  very  im- 
portant, as  it  makes  the  lens  spin  better  and  makes  it  less  likely  to 
get  out  of  center.  Get  into  the  habit  of  changing  the  angle  of  the  pin 
on  each  different  curve,  as  by  doing  this  you  will  grind  and  polish 
more  rapidly  and  with  less  breakage. 

Prisms  are  ground  in  the  same  manner  as  flat  compounds,  with 
the  exception  that  all  prisms  are  thick  at  one  end  and  thin  at  the  other ; 
some  are  ground  so  that  they  will  cut  base  in,  others  base  out,  also 
base  up  and  base  down.  This  is  merely  a  matter  of  grinding  one  side 
of  the  lens  thinner  than  the  other. 

For  example,  if  you  wished  to  make  a  +i-Oo  sph.  +.50  cyl.  axis 
45°  3  2  degree  prism,  base  in,  you  would  proceed  as  follows: 

Mark  as  shown  on  cut  and  grind  the  apex  thinner  than  the  base. 
It  will  be  found  advisable  to  caliper  the  thin  end  and  then  the  thick  end, 
using  the  regulation  caliper  in  degrees  of  one-fifth.  If  the  apex  is 
one  millimeter,  the  base  should  be  three  millimeters ;  or  if  the  prism  be 
one  degree,  the  apex  will  be  one  millimeter  and  the  base  two  milli- 
meters in  thickness,  if  calipering  at  50  millimeters. 

Some  grinders  mark  the  lens  with  the  letter  B  when  the  base  is 
to  be  ground,  and  with  the  letter  E  when  the  apex  is  to  be  ground. 
Every  grinder  developes  a  system  of  his  own  which  he  always  follows. 

When  you  have  a  prism  ground  to  exactness,  make  sure  that  both 


ROUGHING    LENSES  53 

sides  of  the  lens  are  of  the  same  thickness.  Make  yourself  proficient 
in  this  part  of  the  work  before  you  attempt  to  make  a  perfect  lens,  as 
there  are  several  little  tricks  connected  with  grinding  prisms  that 
can  be  acquired  only  by  repeated  practice. 

Wafers,  scales  or  cements,  as  they  are  called,  are  ground  in  the 
same  way  as  the  foregoing,  except  that  they  must  be  ground  to  what 
is  known  as  "knife  edge"  thickness.  This  is  accomplished  by  doing 
more  grinding  with  the  use  of  the  No.  FF  emery,  which  will  not  chip 
the  glass  at  the  edge  as  would  be  the  case  if  a  coarser  emery  were 
used. 

Some  grinders  chip  the  lens  down  to  about  35  or  38  millimeters 
round,  and  then  finish  the  wafer,  or  scale,  to  about  30  or  32  millimeters 
round,  while  others  use  a  larger  lens  and  grind  it  to  any  size  desired. 
When  polishing  scales  it  will  be  well  to  remember  that  you  cannot  use 
much  pressure  on  the  handle,  as  the  scale  will  heat  quickly  and  is 
likely  to  crack  as  a  result.  Never  try  to  "speed  up"  on  scales,  it 
doesn't  pay.  Too  much  pressure  and  leaving  the  lens  on  the  polisher 
will  always  result  in  breakage. 

All  wafers  or  scales  are  made  in  the  same  manner,  and  the  weaker 
the  scales  the  more  is  the  need  for  care  in  handling  them,  especially 
in  making  toric  scales,  in  which  operation  the  greatest  care  must  be 
given  to  every  detail  from  start  to  finish. 


Surfacing  Meniscus  Lenses 

This  brings  you  to  meniscus  lenses,  but  work  on  these  should  not  be 
undertaken  until  you  have  made  yourself  thoroughly  proficient  on  flat 
lenses. 

Every  optical  jobber  handles  rough  drop  or  meniscus  blanks,  which 
come  in  various  thicknesses.  Some  have  a  plus  6.00  curve  and  others 
a  minus  6.00  curve,  ground  and  polished.  The  best  kind  to  use  for 
practice  purposes  is  that  with  the  minus  6.00  curve. 


54  OPTICAL    SHOP    PRACTICE 

To  grind  a  plus  2.00  meniscus  lens,  is  a  simple  matter.  Select  a 
rough  toric  blank  with  a  —  6  base  curve  about  3  millimeters  thick,  and 
grind  a  plus  8.00  curve  on  the  opposite  side. 

To  make  a  meniscus  CC  lens:  Suppose  you  wished  to  grind  a 
minus  4.00  meniscus.  You  would  select  a  rough  toric  blank,  with  the 
plus  6.<x>  curve  ground  on  one  side,  and  then  proceed  to  grind  a  minus 
10.00  curve  on  the  opposite  side. 


Toric  Compounds 

Now  comes  the  grinding  of  toric  compounds,  and  with  this  step 
you  enter  a  stage  of  the  work  which  requires  even  more  caution  that 
the  former  operations.  It  will  not  pay  you  to  attempt  to  grind  the 
cylinder  side,  for  this  can  be  done  more  cheaply  and  accurately  at  the 
factory  where  they  are  made.  Rough  toric  cylinders  are  all  made 
with  the  two  curves  ground  on  the  plus  side  and  come  in  individual 
containers,  plainly  marked,  giving  the  base  curve  and  also  the  focus. 
They  can  be  obtained  in  any  thickness  from  two  to  six  millimeters, 
and  out  of  a  comparatively  small  stock  it  is  possible  to  obtain  any 
combination  that  may  be  desired ;  that  is  plus  on  plus,  minus  on  minus, 
plus  on  minus  and  minus  on  plus.  All  rough  toric  cylinders  are 
molded,  which  leaves  the  inside  hazy,  or  dull,  and  you  should  always 
examine  them  carefully  before  undertaking  to  block  them. 

Supposing  that  you  wish  to  grind  a  toric  compound,  +.25  +.25, 
13^  millimeters  thick.  First  select  a  +.25  rough  toric  cylinder  and 
after  examining  it  carefully  select  a  concave  block  of  approximately 
the  same  curvature. 

These  blocks  always  have  a  — 6.00  curve  in  the  iron  and  are  made 
in  several  different  forms ;  some  are  square,  some  round.  You  will 
quickly  learn  the  advantages  and  disadvantages  of  the  various  kinds 
and  will  adopt  the  kind  that  suits  you  best.  Be  sure  to  have  a  good 
layer  of  cement  between  the  lens  and  the  block,  as  having  the  lens 
too  close  to  the  iron  will  cause  breakage.    Insufficient  cement  means  a 


ROUGHING    LENSES 


55 


greater  strain  at  the  outer  edge  of  the  glass  than  at  the  center,  and 
this  uneven  strain  will  inevitably  mean  breakage. 

We  shall  now  assume  that  you  have  made  proper  preparations  to 
go  on  with  your  work,  the  first  thing  to  do  is  select  the  proper  tool. 
In  this  case  it  will  be  a  minus  5.75,  and  you  will  first  grind  it  to  the 
right  thickness.  Be  sure  that  the  lens  maintains  a  uniform  thickness 
and  do  not  grind  too  far  with  No.  70  emery,  and  after  using  each 
grade  of  emery  be  sure  to  rinse  the  tool  and  sponge  off  before  apply- 
ing the  next.    Keep  the  handle  clean. 

In  case  you  do  the  polishing  with  the  same  tool  on  which  the 
lens  was  ground,  use  a  thin  cloth,  and  do  not  apply  too  much  pressure. 
The  lenses  heat  very  easily  and  if  you  attempt  to  go  too  fast  you  will 
crack  them,  or  the  heat  may  cause  them  to  jump  off  the  block. 

For  other  combinations:  For  example,  with  a  +2.00  +.50  you 
would  select  a  rough  toric  cylinder,  +.50  and  proceed  to  grind  — 4.00 
on  the  inside,  as  shown  herewith : 


Example : 


Example 


Example 


Example : 


Example 


+6.00 

+  6.50 

—4.00 

—.50  —.50 

+6.00 

+6.50 

—7.00 

— 1. 00  +2.00 

+6.00 

+8.00 

— 7.00 

+2.00  —1.50 

+6.00 

+7-50 

—5.50 

+.50  cylinders 

+6.00 

+6.50 

— 6.00 

— 2.00  cylinders 

+6.00 

+8.00 

—8.00 

56  OPTICAL    SHOP    PRACTICE 

In  case  you  have  any  difficult  or  complicated  combinations  to 
miake  you  will  find  it  best  to  let  your  jobbing  house  do  the  work. 

Surfacing  Bifocal  Work 

A  number  of  practical  bifocal  lenses  have  been  put  on  the  market 
during  recent  years.  These  are  carefully  manufactured  and  have 
been  found  very  desirable,  besides  which  there  is  a  big  demand  for 
them,  such  as  the  Kryptok,  and  the  Onepiece  Bifocal. 

The  Kryptok  bifocal  lens  is  one  which  is  made  from  two  different 
indices  of  glass ;  that  is  the  large  body  is  of  crown  glass  and  the  small 
body  of  flint  glass.  The  smaller  piece  of  flint  glass  is  fused  into  the 
larger,  and  this  work  is  so  difficult  that  it  can  only  be  accomplished  by 
those  who  have  had  years  of  experience. 

All  Kryptok  blanks,  either  flat  or  toric,  come  in  individual  con- 
tainers correctly  numbered,  and  are  generally  6  millimeters  thick.  It 
is  imperative  that  an  operator  should  have  in  many  cases  several 
months  of  continued  practice  on  regular  work  before  undertaking  to 
grind  bifocals  and  even  then  it  will  take  some  time  before  he  is  pro- 
ficient in  handling  these. 

It  is  best,  when  you  are  about  to  undertake  to  work  on  these 
lenses,  to  go  to  your  jobbing  house  for  a  few  demonstration  blanks, 
then  practice  on  these  before  starting  on  regular  work.  Make  a 
careful  inspection  of  all  blanks  before  putting  them  on  the  block.  The 
best  way  to  do  this  is  by  wetting  it  and  holding  it  up  to  an  artificial 
light  (gas  being  better  than  electric  light  for  the  purpose).  Look 
closely  for  bubbles  and  scratches. 

Quiz 

1 — What  grinding  materials  are  generally  used?  How  prepared?  How 
applied  ? 


ROUGHING    LENSES  57 

2 — Tell  how  you  prepare  the  lens  before  turning  on  the  power. 

3 — Why  should  the  opposite  sides  of  a  cylindrical  lens  be  equal  in  thickness  ? 

4 — What  should  you  do  while  grinding,  with  the  "mixture"? 

5 — For  example,  if  you  want  to  grind  a  +3.00  spherical  lens,   1^  milli- 
meters thick  what  should  you  do  in  "roughing  out?" 

6 — After  the  roughing  out,  what  comes  next?    What  mixture  do  you  use? 
How? 

7 — How  long  does  it  take  to  remove  the  "pits?"    Is  thickness  important? 
8 — What  is  the  right  mixture  in  the  next  step? 

9 — How  is  a  good  way  to  avoid  scratches?     What  must  you  do  if  there 
are  any? 

10 — What  happens  if  the  mixture  gets  dry? 
11 — Tell  about  the  "finishing  emery;"  describe  operation  with  it. 
12 — What  mixture  do  you  use  for  polishing? 

13 — Describe  the  polishing  cloth.    Tell  with  what  it  is  fastened  and  how. 
14 — What  should  you  do  when  you  see  steam  coming  from  the  lens? 
15 — What  is  a  flat  rough  cylinder?    What  is  their  usual  size  and  thickness? 
16 — How  far  do  you  rough  out  for  the  V^  millimeter  lens? 
17 — Why  should  all  flat  cylinders  be  carefully  examined? 
18 — What  instruments  are  needed  to  measure  the  curve? 
19 — Why  should  you  draw  a  line  on  the  cylinder  side?    What  do  you  use 
for  making  this  line? 

20 — How  do  you  measure  to  locate  the  center? 

21 — What  is  a  lens  called  when  thicker  at  one  point?     What  is  the  right 
method  to  get  a  lens  back  into  center? 

22 — What  thickness  cylinder  is  used  for  a  plus  6.00  curve? 

23 — How  can  "pull"  and  "jump"  be  avoided? 

24 — How  will  the  edge  of  the  lens  appear?    How  will  the  center  appear? 

25— How  do  you  gauge  the  thickness  of  a  concave  lens? 

26 — What  is  tht  most  important  part  in  grinding  flat  compounds? 

27 — How  is  the  pin  in  the  handle  set  for  weak  curves?    For  convex  curves? 
For  concave  curves? 


58  OPTICAL    SHOP    PRACTICE 

28 — Why  is  it  always  necessary  to  change  the  angle  of  the  pin? 

29 — What  is  the  shape  of  a  prism  lens?  How  are  they  marked?  Why  must 
special  care  be  taken  in  grinding  prisms? 

30 — How  are  wafers,  or  scales,  made?  What  pressure  is  needed  in  polishing 
scales? 

31 — What  are  rough  toric  sphericals?    Why  should  they  be  kept  in  stock? 

32 — What  are  rough  toric  cylinders?  How  many  curves  are  on  a  convex 
rough  toric  cyl.?  What  appearance  has  the  rough  part?  What  kind  of  block 
is  used  for  toric  cyls.?    Why  do  so  many  of  these  lenses  break? 

33 — What  are  Kryptok  blanks?  Why  is  great  care  necessary  in  blocking 
them? 


SURFACING    KRYPTOKS 


CHAPTER  IX 

Surfacing  Kryptoks 

The  Kryptok  bifocal  is  a  lens  made  from  two  different  indices  of 
glass ;  that  is,  the  large  body  is  crown  glass  and  the  small  body  is  flint 
glass.  The  smaller  piece  of  flint  glass  is  fused  into  the  crown  glass; 
this  being  complicated  work  which  can  be  properly  performed  only 
t>y  those  who  have  had  years  of  experience. 

All  Kryptok  blanks,  either  flat  or  toric,  come  in  individual  con- 
tainers, correctly  numbered,  and  are  usually  6  millimeters  thick.  Be- 
fore a  person  is  qualified  to  be  called  a  good  Kryptok  bifocal  grinder, 
he  must  have  had  several  weeks  or  months  of  practice  and  experience 
on  regular  work,  and  he  must  have  a  comprehensive  knowledge  of 
just  how  fast  the  different  emerys  cut  and  how  much  thickness  must 
be  taken  off  the  blank  by  each  emery ;  in  short  he  must  be  the  best  man 
obtainable  before  he  should  be  trusted  with  these  valuable  blanks. 

Before  attempting  to  do  this  work  commercially,  it  will  be  well  for 
you  to  ask  your  wholesale  house  for  a  few  demonstration  blanks  and 
on  these  to  practice  carefully  before  you  attempt  to  grind  the  regular 
blank. 

In  putting  these  blanks  on  the  block  great  care  must  be  taken,  and 
by  all  means  see  that  they  are  heated  evenly  and  that  they  are  kept 
from  drafts  of  cold  air.  Thousands  of  blanks  are  broken  through 
carelessness  on  the  part  of  operators  who  do  not  keep  their  eyes  and 
minds  on  the  work.  The  usual  excuse  is  "poor  blank,"  or  "poor 
annealing." 

Another  precaution  that  must  be  carefully  observed  is  to  get  an 


60 


OPTICAL    SHOP    PRACTICE 


ample  layer  of  cement  between  the  glass  and  the  iron  block.  In  this 
part  of  the  work  do  not  allow  yourself  to  become  one  of  these  '7  guess 
it  is  all  right"  fellows.  Before  you  start  grinding  you  should  know 
positively  that  it  is  all  right. 

The  proper  method  to  begin 
grinding  a  Kryptok  blank  is  to  hold 
the  blank  in  the  right  hand  as 
shown  in  illustration  (Fig.  i),  and 
continue  grinding  off  the  segment 
with  No.  70  emery  until  it  is  with- 
in I  point  (5  point  calipers)  from 
the  larger  piece  of  glass,  as  shown 
in  illustration  (Fig.  2).  After  you 
have  ground  the  segment  down  to 
the  surface  of  the  blank,  as  shown 
in  Figure  2,  you  can  use  the  handle 
and  pin  and  let  the  blank  spin,  and 


Fig.   1.— Right  Way. 


the  segment  will  grind  down  evenly 
all  around,  because  you  started 
grinding  in  the  "right  way." 

Do  not  forget  this  good  ad- 
vice— "Start  right  and  be  sure  to 
stop  grinding  with  rough  emery 
before  you  have  ground  the  seg- 
ment down  to  where  it  meets  the 
major  portion,  or  large  piece  of 
glass."  This  operation  requires  a 
great  amount  of  care  and  the  lens 
should  be  taken  off  frequently, 
rinsed  with  clean  water,  and  care- 
fully inspected. 


Fig.  2. — Proper  Grinding. 


Kryptok  blanks  should  never  be  roughed  with  the  top  of  the 
blank  and  the  top  of  the  segment  touching  the  tool  at  the  same  time. 


SURFACING    KRYPTOKS 


61 


Fig.  3.— Wrong  Way. 


There  is  one  thing  sure  and  that  is, 
if  you  grind  as  shown  in  Figure  3, 
you  will  be  unable  to  get  the  proper 
curve  on  the  blank  or  the  size  seg- 
ment you  desire.  Figure  3  shows 
the  "Wrong  Way"  to  begin  grind- 
ing a  Kryptok  blank,  and  there  is 
much  of  this  grinding  being  done 
today. 

You  will  note  that  the  seg- 
ment comes  about  26  millimeters 
wide.  Now  that  you  have  properly 
ground    your   blank   with    No.    70 

emery  as  shown  in  Figure  2,  you  take  the  next  grade  of  emery  No. 

180  and  grind  the  segment  down  to  22  millimeters.     Go  slowly  and 

carefully,  keep  your  eye  on  the  blank,  and  do  not  go  to  sleep  on  the 

job. 

It  may  not  sound  practical  to  grind  so  much  oflf  with  the  No.  180 
emery,  but  you  will  find  that  in  the  long  run  it  pays  to  let  the  finer 
grades  of  emery  do  most  of  the  work.  The  whole  matter  resolves 
itself  down  to  this  rule;  ''Take  more  time  and  take  fewer  chances^ 
which  is  only  another  way  of  saying,  "slow  but  sure."  The  results 
obtained  through  taking  every  precaution  will  soon  be  manifest  in 
greater  satisfaction  and  financial  return. 

After  grinding  the  segment  down  to  22  millimeters  with  No.  180 
emery,  use  the  No.  FF  emery  and  grind  down  to  2 1  millimeters ;  next 
with  the  finishing  emery  to  20^  or  20. 

Unclean  handles,  dirty  emery  and  careless  methods  in  keeping  the 
rough  emery  will  inevitably  result  in  scratches  and  big  pits.  Hundreds 
of  blanks  are  wasted  daily  and  weekly  from  these  preventable  causes. 
A  system  of  orderliness,  carefully  followed  from  the  beginning,  will 
make  you  a  better  and  far  more  valuable  operator. 


Where  the  additions  are  weak,  3ay  from  -I-0.50  to  -f-i.oo  added, 


62  OPTICAL    SHOP    PRACTICE 

or  in  other  words  Kryptok  blanks  No.  i  to  No.  21  in  the  flat  series 

and  No.  300  to  No.  322  in  the  toric  series,  there  is  great  ''Danger"  of 

grinding  away  the  segment  if  you  are  not  very  careful,  due  to  the 

shallow  curvature  of  the  countersink  in  which  the  flint 

is  fused.    For  instance  No.  i  and  300  blanks  have  such 

Nfti  a  shallow  countersink  that  it  is  hardly  discernible  look- 

N«2i  ing  through  the  edge  of  the  blank,  but  on  No.  43 

ga^^ ,         a"d  344  blanks  it  is  very  discernible  looking  through 

the  edge  of  the  blank,  because  it  is  very  much  deeper. 
N9300  S^^  illustration  Figure  4  and  take  all  the  precautions 

possible  to  avoid,  grinding  the  segments  too  small. 

Never  use  No.  70  emery  on  any  of  these  numbers, 
but  start  grinding  with  No.   180  emery,  leaving  the 

segment  the  full  26  milHmeters  wide,  then  g-rind  it 
Fig.  4. 

down  to  24  millimeters  with  No.  FF  emery,  then  fin- 
ish it  with  extra  fine  emery. 

This  method  is  somewhat  slower,  but  so  many  grinders  are  in- 
clined to  rush  things  that  this  will  be  found  the  better  and  safer 
method,  with  less  chance  of  getting  the  segment  too  small.  Nearly 
all  the  expert  (and  consequently  high  priced),  grinders  throughout 
the  country  use  this  slow,  careful,  accurate  and  common  sense  method. 

The  selection  of  Kryptok  blanks — that  is",  the  proper  number  for 
a  given  prescription — has  become  an  important  part  of  surface  grind- 
ing. These  blanks  are  to  be  had  at  all  wholesale  optical  houses,  and 
are  supplied  in  individual  containers,  correctly  marked  and  numbered. 
If  the  operator  will  devote  a  little  time  to  the  study  of  transposition, 
errors  of  focus  will  be  reduced  to  the  minimum. 

Before  commencing  to  grind  Kryptoks  you  should  write  to  your 
jobber  for  a  chart,  both  for  toric  and  flat  blanks.  This  is  supplied 
free  of  charge  and  it  is  impossible  to  grind  Kryptok  jobs  without  the 
chart.  When  you  receive  it  get  right  down  to  business  and  learn 
how  to  use  it. 

It  is  absolutely  necessary  in  order  to  obtain  proper  results  in 


SURFACING    KRYPTOKS  63 

finished  Kryptok  lenses,  to  follow  the  Kryptok  chart  accurately.  If, 
according  to  your  prescription  the  chart  calls  for  a  326  blank,  do  not 
use  324  blank.  If  your  prescription  calls  for  348  blank,  do  not  use 
346,  because  if  you  do  you  are  sure  to  have  off  focus  trouble.  It  is  a 
very  easy  matter  to  select  the  wrong  blank,  if  you  are  not  careful  in 
consulting  the  Kryptok  chart. 

In  other  words  don't  juggle  Kryptoks.  Don't  use  any  blank 
except  the  exact  number  that  the  chart  calls  for,  and  never  use  a  300 
series  blank  for  a  200  series  blank,  or  vice  versa.  Any  curve  given  on 
the  Kryptok  chart  on  torics  can  be  ground  according  to  the  curve 
designated. 

Now  let  us  consult  the  Kryptok  chart  on  a  few  prescriptions: 

For  example;  +2.00  sphere  add  +2.00  flat  Kryptok.  In  looking 
at  the  chart  you  will  note,  under  the  sub-head  "Flat  Kryptoks,"  that 
the  number  of  the  blank  for  add  +2.00  is  No.  43;  therefore  grind 
piano  on  the  segment  side  and  -{-2.00  sphere  on  the  opposite  side,  and 
this  will  make  the  lens  perfect  in  focus. 

Example;  +3.00  sphere  add  -f  i.oo,  flat  Kryptok.  To  add  +i-00 
you  will  note  the  chart  tells  you  to  take  No.  21  blank.  Grind  piano 
on  the  segment  side  and  +3.00  on  the  opposite  side. 

Example;  — i.oo  sphere  add  +3.00,  flat  Kryptok.  For  an  add 
+3.00  the  chart  will  tell  you  that  No.  65  blank  is  required.  Grind 
piano  on  the  segment  side  and  — i.oo  sphere  on  the  opposite  side. 

It  is  absolutely  necessary  at  all  times  whether  you  grind  plain 
spheres  or  compounds,  that  you  use  the  exact  number  given  on  the 
chart;  the  only  difference  is  that  on  spheres  you  have  a  choice — that 
is  to  say  for  a  -f-^oo  sphere  you  can  grind  a  piano  on  the  segment 
side,  or  you  can  grind  +i-00  on  the  segment  side,  and  if  you  desire 
you  can  also  grind  a  +0.50  on  the  segment  side ;  the  difference  in  the 
sphere  will  be  made  up  by  the  curvature  on  the  opposite  side. 

This  does  not  mean,  however,  that  the  same  blank  number  can  be 
used  for  each  of  these  combinations  of  curves.    A  different  blank  num- 


64 


OPTICAL    SHOP    PRACTICE 


ber  is  used  for  each  curve.  For  proper  blanks  and  curves  consult 
Kryptok  chart. 

Now  we  will  consider  the  grinding  of  Kryptok  compound  lenses. 
For  instance:  +2.00  sph.  C  with  +0.50  cyl.  axis  180  add  -\-2.00. 
You  will  note  that  on  the  left  side  of  the  chart  are  shown  the  curves 
to  be  ground  on  the  segment  side  of  the  blank.  The  curve  required 
is  +2.00  sphere;  trace  down  the  column  on  the  left  side  of  the  chart 
until  you  come  to  +2.00  sphere,  then  trace  across  to  the  column  marked 
"add  2.00.*'  You  will  find  the  blank  for  that  combination  is  No.  35. 
Grind  +2.00  sph.  on  the  segment  side  and  grind  +0.50  cyl.  on  the 
opposite  side. 

To  make  the  following  combinations;  +2.50  sph.  combined  with 
+0.50  cyl.  axis  90,  add  +2.00  the  chart  will  tell  you  that  blank  No.  33 
should  be  used.  Grind  +2.50  sph.  on  the  segment  side  and  +0-50 
cyl.  on  the  opposite  side. 

The  beginner  should  start  with  spherical  work,  which  will  give 
the  valuable  practice  and  experience  that  are  necessary  before  taking 
up  compound  or  cylinder  grinding. 


Right  Eye 


Left  Eye 


NOTE. — This  illustration  is  not  as  thougrh  ths  lenses  were  finished  and  on  the 
patient,  but  just  the  opposite,  as  laid  out  on  a  protractor.  Being  prepared^  or 
markei.'.  for  the   surfacing  of  the   other  side. 

One  important  part  will  come  to  your  attention,  viz;  that  after 
the  segment  side  of  the  blank  is  ground,  the  top  of  the  segment  may 
be  too  high  or  too  low.     A  good  way  to  overcome  this  is  to  lay  the 


SURFACING    KRYPTOKS 


65 


blank  (after  the  first  side  is  finished),  on  a  protractor  card,  which  your 
optical  house  will  supply  free  of  charge.  Get  the  top  of  the  segment 
I,  2  or  3  millimeters  (as  the  case  may  require)  below  the  optical 
center  of  your  distant  lens,  and  also  decenter  segments  in  on  each 
eye  as  required.  Usually  segments  are  set  in  on  each  eye  from  i 
to  2  millimeters.  The  centers  of  the  reading  discs  should  never  be 
placed  on  the  vertical  distance  center  line  for  the  pupillary  measure- 
ment, for  distance  is  not  the  same  as  that  for  reading.  The  proper  way 
to  lay  out  Kryptok  blanks  for  cylinder  grinding  is  shown  in  our  illus- 
tration above  (Fig.  5),  it  is  also  necessary  in  order  to  get  the  best 
results,  to  take  into  consideration  the  size  of  the  finished  lens  and  to 
allow  about  3  millimeters  larger  all  around  the  rough  blank  and  chip 
away  the  unnecessary  glass  before  grinding  the  cylinder  side. 

If  you  are  going  to  grind  a  compound  lens,  it  will  'be  necessary  to 
mark  the  base  curve  of  the  cylinder  or  in  other  words,  the  axis  of  the 
cylinder,  also  prism  marking  the  apex  and  base,  if  a  prism  is  to  he 
ground. 

If  the  blank  is  not  properly  marked  before  the  cylinder  is  ground, 
it  will  be  impossible  after  the  cylinder  has  been  ground  to  get  the 
proper  axis,  location  and  decentration  of  segments. 

In  grinding   flat  Kryptoks, 

^o1/h ^  ^j^g  greatest  care  must  be  given 

to  watch  the  thickness — that 
part  over  the  segment.  If  you 
have  a  strong  addition  and  make 
a  large  size  segment,  it  will  re- 
quire a  thick  lens.  A  good  way 
to  determine  the  exact  thickness 
that  you  can  grind  is  to  edge  the 
bottom  of  the  lens  where  the 
segment  is  fused  in,  then  when  you  are  grinding  down  you  can  hold 
the  lens  up  to  the  light  and  looking  through  the  edge  you  will  soon 
learn  to  distinguish  between  the  bottom  of  the  crown  glass  and  the 
top  of  the  flint  glass,  or  vice  versa.    This  precaution  should  always 


Fig.    6. — Grinding    Thicknesses. 


OPTICAL    SHOP    PRACTICE 

be  taken  when  grinding  prescrip- 

Ground  Tdd  Thin     *'""'  *^.*  '^"''■^  ^"'^"^  ^'""''^ 

on  both  sides,  or  where  the  concave 
curve  is  greater  than  the  convex 
c^^  ^  —^^^^^^  curve.  While  grinding  the  edge  of 
TDRiC  ^^^  blank  to  see  how  far  you  are 
grinding  is  a  good  way,  neverthe- 
less a  better  way  is  to  know  ex- 

._  ,  actly  how  much  cflass  is  necessarv 

for  thickness  on  various  additions. 
FLAT  (See  Fig.  6.) 

Fig.  7. 

Much    of    the    disappointment 

of  customers,  much  of  your  lost  labor,  time  and  temper,  is  caused  by 
grinding  through  the  opposite  side  of  your  Kryptok  blank.  This,  of 
course,  takes  place  after  the  segment  side  has  been  finished.  The 
accompanying  diagram  (Fig.  7)  illustrates  the  appearance  of  Kryptok 
blanks  when  ground  through  the  segment,  or  in  other  words,  when 
it  is  ground  too  thin.  The  small  circle  in  the  large  blank  shows  where 
the  flint  is  ground  through  from  the  opposite  side.  You  will  also 
notice  on  the  toric  and  flat  blank,  that  the  curve  on  the  countersink  is 
broken,  thus  showing  the  blank  was  ground  too  thin. 

Take  for  instance  the  illustra- 
WA5CRDL1ND  *^^"    ^^^^'   ^^    ^^^*   shows   a   lens 

|iM/    THICK-WHYP   ^^^^  ^  +3-00  diopter  added,  that 
8      M  finir    ^^^  ground  i>4  miUimeters  thick, 

.   ^  _^  ^     but    should    have    been    ground    2 

millimeters  thick.     Why  was  this 

'     lens  ground  i^^l  millimeters  instead 

SHDULD  HAVE  BEEN        of  2  millimeters?    First  of  all  the 

GROUND  2  ^  THICK     grinder  may  be  careless  and  this 

would  be  the  result.     Second,  the 
,     wrong  curve  may  have  been  ground 


_.     ^  on  the  blank,  and  trying  to  correct 

Fig.  8.  'JO 

the  error,  he  ground  the  blank  too 
thin.    Third,  the  operator  may  not  know  the  proper  thickness  to  leave 


SURFACING    KRYPTOKS  67 

the  blank  on  the  various  additions,  and  if  this  is  the  case,  consult  illus- 
tration on  thicknesses  (Fig.  6). 

A  large  number  of  blanks  are  spoiled  daily  owing  to  the  fact  that 
the  grinder  is  not  careful  to  observe  the  little  precautions  that  help 
to  make  a  job  efficient.  When  blanks  are  "ground  through" — that  is 
when  the  crown  is  ground  down  to  meet  the  flint — it  is  merely  a  result 
of  too  much  haste  on  the  part  of  the  operator  who  neglects  to  use 
the  necessary  care  in  his  work — and  the  result  is  that  the  cost  of  the 
blank  is  lost  as  well  as  the  time  that  it  takes  to  grind  both  sides. 

Toric  Kryptoks 

The  selection  of  toric  Kryptok  blanks  is  worked  out  in  much  the 
same  manner  as  the  method  use  in  flat  Kryptoks.  However,  there  is 
one  exception  that  must  always  be  taken  into  consideration,  viz. :  that 
all  plus  on  plus,  or  minus  on  plus  combinations  must  invariably  he 
transposed.  The  reason  for  this  is  that  the  cylinder  can  never  be 
ground  on  the  segment  side.  With  toric  blanks,  as  with  flat,  many 
different  combinations  can  be  made  from  one  particular  number.  It 
will  be  necessary  for  the  operator  who  selects  the  Kryptok  blank  to 
know  how  to  transpose  and  we  will  give  here  a  few  rules  and  examples 
on  transposition.  Take  for  instance  a  +i-0O  sphere  combined  with 
a  +I.OO  cylinder  axis  90,  transposed  it  will  be  +2.00  sphere  — i.oo 
cylinder  axis  180.  In  other  words  on  plus  on  plus  prescriptions  you 
add  the  power  of  both  the  sphere  and  the  cylinder  together  for  your 
sphere  and  add  to  it  a  cylinder  of  the  same  pK>wer  but  opposite  sign 
and  axis.  Then  take  another,  for  instance,  a  +1.75  sphere  combined 
with  a  +2.25  cylinder  axis  25;  transposed,  it  will  be  +4.00  sphere 
— 2.25  cylinder  at  axis  115. 

In  transposing  minus  on  plus  where  the  cylinder  power  is  greater 
than  the  spherical  power,  you  subtract  the  sphere  from  the  cylinder 
and  the  remainder  is  proper  sphere,  combine  this  with  a  cylinder  of 
the  original  power  but  opposite  sign  and  axis. 


OPTICAL    SHOP    PRACTICE 
TRANSPOSITION 


]^    +I.OO 
+  I.OO 


+  I.OO  Axis  90° 


+2.00  = 

— 1 .00 

Axis 

180° 

5  +1.25  = 

—2.25 

+1.25 

Axis  60° 

— 1.00  = 

+2.25 

Axis 

150° 

^  +2.25  = 

— 1 .00 

— 1. 00 

Axis 

75° 

+1.25  = 

+1.00 

Axis 

165° 

^  —1.75  = 
—1.25 

—1.25 

Axis 

10° 

?  —3.00 

+1.25 


+1.25  Axis  65* 


-1.75=— 1.25  Axis  155* 


^  -1.75 


+2.25  Axis  25* 
—1-75 


+0.50  =  — ^2.25  Axis  115' 


I^   +0.50  Axis  80' 


4-50== — 50  Axis  170' 


1^  — 1. 00  Axis  95' 


-1.00= +1.00  Axis  5' 


-3.00  =+1.25  Axis  100° 


The  safe  rule  to  follow  is :  The  stronger  the  curve  on  the  segment 
side,  the  stronger  the  addition  will  he.    For  example: 

No.  338  blank,  with  plus  6,00  curve  ground  on  the  segment  side, 
will  give  an  addition  of  plus  1.75 ;  if  you  grind  plus  7.50  on  the  blank,  it 
will  give  an  addition  of  plus  2.00 ;  if  you  grind  plus  8.75  on  the  blank, 
it  will  give  an  addition  of  plus  2.25.  This  rule  holds  good  on  all  blanks. 

The  following  examples  will  help  you  in  making  the  proper  trans- 
positions, and  will  help  you  select  the  right  blank.  This  is  by  no  means 
a  complete  list: 

No.  1  Pkis    .25  combined  with  plus        .25  axis    90  add  2.00 

No.  2  Plus    .50  combined  with  plus        .50  axis  180  add  2.50 

No.  3  Plus  1.00  combined  with  plus      1.00  axis    90  add   1.50 

No.  4  Plus    .50  combined  with  minus    .25  axis    90   add   1.75 

No.  5  Plus  2.00  combined  with  minus  1.00  axis  180  add  2.00 

No.  6  Plus  3.00  combined  with  minus  2.00  axis    90  add  3.50 

No.  7  Minus  1.00  combined  with  minus  1.00  axis    90  add  1.00 

No.  8  Minus  3.00  combined  with  minus    .50  axis    90  add  2.00 

No.  9  Minus  2.50  combined  with  minus  1.00  axis  180  add  3.00 


SURFACING    KRYPTOKS 


No.  10  Minus  .50  combined  with  plus 
No.  11  Minus  3.50  combined  with  plus 
No.  12  Minus  4.00  combined  with  plus 

The  above  should  be  ground  as  follows: 


1.00  axis  180  add  2.50 
4.50  axis  90  add  1.00 
2.00  axis  180  add  2.00 


No. 

Segment  Side 

Opposite 

Side 

Blank  No. 

1 

plus 

6.50 

Minus 

6.00 

Minus 

6.25 

342 

2 

plus 

7.00 

Minus 

6.00- 

Minus 

6.50 

350 

3 

plus 

8.00 

Minus 

6.00 

Minus 

7.00 

325 

4 

plus 

6.50 

Minus 

6.00 

Minus 

6.25 

336 

5 

plus 

«.00 

Minus 

6.00 

Minus 

7.00 

336 

6 

plus 

9.00 

Minus 

6.00 

Minus 

8.00 

842 

7 

plus 

5.00 

Minus 

6.00 

Minus 

7.00 

215 

8 

plus 

3.00 

Minus 

6.00 

Minus 

6.50 

245 

9 

plus 

8.50 

Minus 

6.00 

Minus 

7.00 

265 

10 

plus 

6.50 

Minus 

6.00 

Minus 

7.00 

352 

11 

plus 

7.00 

Minus 

6.00 

Minus 

10.50 

318 

12 

plus 

4.00 

Minus 

6.00 

Minus 

8.00 

241 

All  blanks  from  No.  i  to  No.  io8  are  flat  on  both  sides;  from 
No.  418  to  No.  516  are  minus  2.00  on  segment  side  and  flat  on  the 
opposite  side;  from  No.  626  to  721  are  minus  4.00  on  segment  side 
and  flat  on  the  opposite  side;  from  No.  200  to  287  are  plus  3.00  on 
segment  side  and  minus  6.00  on  the  opposite  side;  from  No.  300  to 
387  are  plus  6.00  on  segment  side  and  minus  6.00  on  the  opposite  side ; 
from  No.  800  to  No.  874  are  plus  9.00  on  segment  side  and  minus  6.00 
on  the  opposite  side. 

There  is  considerable  danger 
in  grinding  the  wrong  curve  on 
Kryptok  blanks,  especially  is  this 
the  case  in  torics.  Grinding  wrong 
curves  on  the  Kryptok  blank  is 
very  serious  and  evidently  there 
are  many  wrong  curves  being 
ground  today.  The  opposite  cut, 
(Fig.  9)  well  illustrates  how  the 
wrong  curve  has  'been  ground  on 
the  blank  with  rough  emery  which 
is  shown  by  the  outer  grain  on  our 


Wrong  Curve  Grduno 


RDUGH 

emery 


FINE 
EMERY 


70  OPTICAL    SHOP    PRACTICE 

picture,  and  when  the  operator  tries  to  fine  it  up  with  the  proper  tool, 
this  is  the  result. 

By  this  kind  of  grinding  you  will  be  unable  to  get  the  size  lens 
that  you  want,  and  the  size  of  the  segment  will  also  be  too  small,  and 
in  all  probability  it  will  be  a  disappointment  to  the  customer.  Try  to 
eliminate  this  expensive  negligence  and  carelessness. 

This  can  be  avoided  by  making  it  a  rule  to  gauge  your  tool  before 
using  it  to  see  that  you  have  the  proper  curve  on  your  tool. 

Right  here  is  a  good  place  to  point  out  some  of  the  errors  that 
have  been  made  hundreds  of  times  by  grinders.  Ninety-nine  times  in 
a  hundred  these  attempts  have  failed;  therefore, 

Don't  grind  a  cylinder  on  the  segment  side  of  a  Kryptok  blank. 

Don't  mark  the  polished  surface  of  a  Kryptok  lens  with  India  ink 
or  any  other  ink  that  will  stain  glass. 

Don't  use  coarse  emery  on  weak  additions. 

Don't  try  to  put  a  minus  2.50  curve  on  a  No.  42  blank.  The 
segment  will  always  be  too  small.  Select  a  No.  442 — that  is  the  sure 
way  to  get  a  large  size  segment. 

Don't  try  to  get  a  plus  5.00  curve  on  a  flat  blank.  The  segment 
will  be  too  small  and  the  blank  will  be  too  thin  at  the  top. 

Don't  try  to  grind  a  plus  6.50  curve  on  a  No.  245  blank.  The 
blank  will  be  too  thin  in  the  center. 

Don't  try  to  grind  a  plus  9.50  curve  on  a  No.  353  blank.  Usuary 
the  segment  will  be  too  small  and  the  blank  will  be  too  thin  at  the  top. 

Don't  try  to  grind  a  plus  7.00  curve  on  a  No.  852  blank.  The 
segment  will  be  too  small. 

These  experiments  have  been  made  so  often,  only  to  be  followed 
by  failure,  that  it  will  be  found  advisable  always  to  order  such  special 
blanks  from  your  jobber.  All  standard  blanks  are  made  from  perfectly 
white  crown  glass.  All  colored  blanks,  and  also  those  not  standard 
size,  are  made  special. 

The  standard  size  segment  is  19  millimeters,  although  some  opti- 


SURFACING    KRYPTOKS  71 

cians  require  them  larger  and  others  smaller  than  that  size.  The 
advantage  found  in  using  a  small  segment  is  that  you  can  get  a  thinner 
lens.  Where  the  additions  are  strong,  say  2.75  to  3.50,  it  will  be  well 
to  make  the  segments  as  small  as  18  millimeters. 

If  care  be  used  in  selecting  the  blanks,  getting  the  proper  block 
and  the  correct  degree  of  heat,  and  giving  utmost  attention  in  the 
grinding  and  polishing  operations,  one  should  readily  become  an  expert 
grinder  of  Kryptoks. 


Quiz 

1 — What  is  a  Kryptok  Bifocal  lens?    Describe  briefly  its  construction. 

2 — Is  it  an  easy  matter  to  become  a  Kryptok  Bifocal  grinder?     Why? 

3 — What  caution  must  be  observed  relative  to  putting  them  on  the  block? 

4 — What  about  the  cement? 

5 — State  the  proper  method  of  beginning  to  grind  a  Kryptok  Bifocal  lens. 
What  emery  is  used? 

6 — What  do  you  do  after  the  segment  is  ground? 

7 — Describe  the  method  of  grinding  which  must  be  avoided.  Why  is  it 
wrong  ? 

8 — What  is  the  procedure  after  grinding  down  with  No.  70  emery? 

9 — Has  cleanliness  anything  to  do  with  good  results?     Why? 

10 — Tell  why  care  must  be  exercised  in  grinding  Kryptok  Bifocals,  regarding 
the  segments. 

11 — Describe  the  last  steps  in  grinding. 

12 — Why  is  it  important  to  have  a  chart? 

13 — What  is  necessary  to  follow  whether  you  grind  plain  spheres  or  com- 
pounds ? 

14 — With  what  kind  of  work  should  the  beginner  start?     Why? 

15 — What  important  point  will  you  notice  after  the  segment  of  the  blank 
is  ground? 

16 — How  do  you  overcome  this? 

17 — What  is  necessary  to  do  if  a  compound  lens  is  to  be  ground? 

18 — What  is  the  case  if  the  blank  is  not  properly  marked  before  the  cyl.  is 
ground  ?  ■  •  ,' 


72  OPTICAL    SHOP    PRACTICE 

19 — What  caution  must  be  taken  in  grinding  flat  Kryptoks? 

20 — What  is  a  good  way  to  determine  the  exact  thickness  that  you  can  grind  ? 

2J — What  frequently  causes  much  annoyance  in  grinding  Kryptok  blanks? 

22 — What  exception  must  be  made  in  selecting  toric  Kryptoks? 

23 — What  is  necessary  for  the  operator  who  selects  Kryptok  blanks  to 
know? 

24 — How  do  you  transpose  minus  on  plus  where  the  cylinder  power  is  greater 
than  the  spherical  power? 

25 — What  is  the  safe  rule  to  follow  in  transpositions?  Does  it  apply  t© 
all  blanks? 

26 — Describe  blanks  from  No.  1  to  108,  as  regards  both  sides ;  from  No.  418 
to  No.  516;  from  No.  626  to  No.  721;  from  No.  200  to  No.  287;  from  No.  300 
to  No.  387 ;  from  No.  800  to  No.  874. 

27 — In  what  special  kind  of  Kryptoks  is  there  danger  of  grinding  the  wrong 
curve? 

28 — What  results  from  the  wrong  method  of  grinding?  How  can  you  avoid 
the  same? 

29 — Enumerate  some  errors  often  made  by  grinders  working  on  Kryptoks. 

30 — What  is  the  best  thing  to  do,  so  as  to  avoid  such  mistakes? 

31 — What  kinds  of  blanks  are  made  special? 

32 — What  is  the  standard  size  segment? 

33 — What  is  the  advantage  in  using  a  small  segment? 

34 — What  is  it  best  to  do  where  the  additions  are  weak? 


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SURFACING    ULTEX,    ONEPIECE    BIFOCAL    LENSES 


73 


CHAPTER  X 

Surfacing  Ultex,  Onepiece  Bifocal  Lenses 


As  is  well  known  to  the  up  to  date  surface  grinder,  the  Ultex 
onepiece  blank  comes  to  the  shop  with  the  Bifocal  side  all  ground  and 
polished.  Thus,  it  is  only  necessary  to  grind  and  polish  the  one  sur- 
face, and  that  a  comparatively  easy  operation. 

The  method  of  procedure  is  very  simple.  Consult  your  prescrip- 
tion in  order  to  ascertain  the  proper  blank  and  tool  to  use  for  the  job. 
Two  charts  are  supplied  by  the  manufacturers,  both  being  alike  in 

principle,  but  one  calling  for  blanks 
ground  to  — 4.,  — 6.,  and  — 8.  base 
curves,  and  carrying  262  tools,  while 
the  other  calls  for  blanks  ground  only 
to  — 6.  and  — 8.  base  curves,  with 
nearly  twice  the  number  of  tools.  The 
former  cuts  down  the  investment  in 
tools ;  the  latter  cuts  down  the  invest- 
ment in  blanks.  The  latter  chart  is 
/  \       the  more  satisfactory,  in  every  way, 

as  tools  are  less  expensive  than  blanks, 
and    furthermore,    the    deep    curved 
form  of  lens,  with  its  consequent  large  field  of  vision,  is  maintained. 

After  noting  the  prescription  to  be  ground,  look  it  up  in  the  chart 
to  ascertain  the  proper  blank  and  tool  to  use.  For  example :  suppose 
the  prescription  reads  +1.25  +1.00,  add  +2.00.  Consult  the  +  C  + 
section  of  the  chart,  we  run  down  the  sphero  column  until  we  come 
to  +1.25 ;  then  run  along  this  column  horizontally  until  we  come  under 
the  required  cylinder  power  —  in  this  case  +1.00.  At  the  intersection 
or  crossing  of  the  +1.25  horizontal  column  and  the  +1.00  vertical 


FIfl.  1. 


74  OPTICAL    SHOP    PRACTICE 

column,  we  find  that  a  — 6.  base  blank  is  called  for,  and  a  7.25  x  8.25 
toric  tool.  Suppose  the  prescription  to  have  been  — 1.25  +1.00,  add 
4-2.00;  consult  the  —  3  +  section  in  the  same  manner,  and  we  find 
that  — 8.  base  blank  and  a  6.75  x  7.75  tool  are  required. 

Next,  select  a  blank  of  the  required  base  curve  and  having  the 
proper  addition.  Crumb  the  blank  to  the  approximate  size  and  shape 
of  the  finished  lens.  This  will  save  a  lot  of  unnecessary  grinding  and 
polishing  and  also  allow  the  lens  to  be  brought  down  to  proper  thick- 
ness without  grinding  the  edges  unduly  thin,  as  is  frequently  the  case 
when  a  full  size  blank  is  used.  Attention  to  this  matter  will  save  a 
lot  of  breakage. 

Next,  locate  and  dot  the  required  position  for  the  optical  center 
of  the  distance  portion,  also  the  axis  of  the  cylinder,  if  any,  decentering 
in  the  reading  portion  the  required  amount.  The  customary  practice 
is  to  decenter  each  segment  13^  m/m,  swinging  it  in  this  amount,  using 
the  optical  center  of  the  distance  portion  as  a  pivot.  This  should  be 
done  before  marking  up  the  axis.  Then  mark  up  four  measuring 
points  on  the  lens  as  shown  in  Fig.  i .  The  reason  for  this  arrangement- 
is  obvious,  as  the  segment  for  reading  portion  is  raised  above  th.^ 
distance  portion  so  that  in  measuring  for  thickness  we  must  avoid 
the  segment  and  measure  on  either  side  of  it,  as  shown  in  the  cut. 

Block  up  the  blank,  using  as  large  an  iron  blank  as  possible.  The 
reason  for  this  is  that  if  the  lens  extends  too  far  beyond  the  edge  of 
the  block,  breakage  is  apt  to  result.  The  layer  of  pitch  between  lens 
and  block  should  be  of  uniform  thickness  at  all  points.  That  is,  the 
convex  curve  on  the  iron  blank  should  be  of  the  same  curvature  as 
the  concave  curve  on  the  lens  blank.  If  one  is  +6.,  the  other  should 
be  — 6.,  and  the  layer  of  pitch  should  be  about  3  m/m  thick.  Attention 
to  above  points  will  save  a  lot  of  breakage. 

When  roughing  the  blank  down,  follow  exactly  the  same  methods 
you  would  use  finishing  the  second  surface  of  a  single  vision  lens.  If 
emery  is  used  for  roughing,  use  60  grade;  if  Alundum  or  Aloxite, 
use  70  or  80  grade.     Rough  to  within  3/10  m/m  of  final  thickness. 


SURFACING    ULTEX,    ONEPIECE    BIFOCAL    LENSES  75 

Smooth  with  *' factory"  smoothing  emery,  ordinarily  known  as  302, 
taking  off  1/5  m/m  in  smoothing.  Run  the  smoothing  emery  dead, 
and  then  finish  with  finishing  emery,  as  furnished  by  the  factories. 
Run  the  finishing  emery  black,  or  dead,  but  be  careful  that  the  lens 
surface  does  not  come  in  contact  with  the  tool. 

Polish  with  "wet  ground"  rouge,  as  furnished  by  the  factories. 
It  costs  a  little  more,  but  will  not  scratch.  One  scratched  Ultex  is 
equal  in  value  to  a  lot  of  rouge,  and  it  is  false  economy  to  use  the 
"dry  ground"  rouge  on  high  priced  lenses.  Use  the  thinnest  possible 
polishing  cloth ;  billiard  table  cloth  is  best,  if  it  can  be  obtained.  Stick 
cloth  to  tool  with  a  mixture  of  resin  and  turpentine.  This  mixture 
holds  better  than  resin  and  naphtha,  and  should  be  used  as  thick  as 
possible.  Run  polisher  fairly  dry  and  sticky,  in  order  to  produce 
friction  and  consequent  rapid  polishing.  Do  not  get  the  lens  too  hot — 
haste  makes  waste. 

Use  your  head  and  exercise  care,  and  thus  save  time  and  expense. 

Quiz 

1 — How  many  sides  are  ground  on  an  Ultex? 

2 — What  method  is  used  to  get  proper  number  of  blanks? 

3 — Where  are  charts  procured? 

4 — How  many  different  base  curves  arc  used? 

5 — What  size  and  shape  are  best  for  grinding? 

6 — What  is  the  result  of  using  extra  large  blanks? 

7 — How  do  you  locate  the  optical  center? 

8 — What  method  is  used  for  finding  axis  of  cylinder? 

9— What  is  the  customary  practice  for  decentering  lenses? 

10— Why  should  this  be  done  before  marking  up  axis? 

11 — How  many  measuring  points  should  be  used?  ■ 

12 — What  should  be  avoided  in  measuring? 

13— What  size  iron  block  should  be  used? 

14 — What  result  could  be  expected  in  using  smaller  blocks? 

15— Why  should  the  layer  of  pitch  be  uniform  in  thickness? 


76  OPTICAL    SHOP    PRACTICE 

16 — What  grade  of  emery  is  used  for  roughing? 
17 — How  thick  should  a  lens  be  when  the  rough  emery  is  used? 
18 — What  number   emery  should  be  used   for  the  second,   or   smoothing, 
operation  ? 

19 — How  much  thickness  will  come  off  with  this  smoothing  operation? 

20 — What  is  the  last  grade,  or  finishing  emery? 

21 — Why  do  you  run  this  finishing  emery  black? 

22 — Why  should  extraordinary  care  be  used  with  the  finishing  emery? 

23 — What  is  the  usual  way  to  poHsh  Ultex  lenses? 

24 — What  thickness  of  cloth  is  the  best? 

25 — How  is  the  polisher  cemented  to  the  iron  disc? 

26 — What  extraordinary  care  should  be  used  in  polishing? 


SOLDERING    AND    REPAIRING  77 


CHAPTER  XI 

Soldering  and  Repairing 

The  average  optician  does  not  do  much  practicing  in  the  way  of 
soldering.  Of  course  from  a  commercial  standpoint  it  is  the  best  way 
for  the  optician  to  endeavor  to  sell  new  goods,  but  if  he  isn't  in  a 
position  to  repair  old  ones  where  a  sale  of  the  new  is  impossible  he 
is,  to  use  a  common  phrase,  "up  against  it."  Therefore  it  is  by  all 
means  advisable  to  master  the  art  of  soldering  broken  frames  and 
mountings,  so  in  case  an  emergency  arises  he  is  not  in  a  predicament. 

While  it  is  true  that  alcohol  lamps  are  often  used  in  this  work, 
the  popular  agency  used  is  gas,  for  various  reasons.  Suffice  to  say 
that  those  who  have  been  at  this  work  for  years  prefer  gas,  so  there 
must  be  a  good  reason  for  their  preference.  In  order  to  concentrate 
the  heat  on  one  spot  a  blowpipe  is  used,  and  you  can  get  sufficient 
service  out  of  an  ordinary  small  mouth  blowpipe  about  }i  of  an  inch 
in  diameter  and  8  or  ten  inches  long. 

There  are  various  styles  of  solder  blocks,  but  charcoal  seems  to 
be  used  most  by  the  better  grade  of  repair  men.  It  might  be  stated 
here,  however,  that  after  you  have  become  reasonably  proficient  in 
soldering  you  will  never  use  a  block. 

A  very  important  factor  in  this  work  is  a  borax  slate.  This  is 
simply  a  block  of  slate,  concave  in  the  center,  which  is  used  for  mix- 
ing the  soldering  solution.  Borax,  of  which  the  solution  is  made,  is 
sold  in  a  number  of  different  forms.  To  mix  the  solution  apply  a  few 
drops  of  water  in  the  depression  in  the  slate  and  rub  the  cake  of  borax 
in  this  until  you. obtain  a  thick  milky  liquid.  Be  sure  that  before  using 
this  cake  of  borax  you  soak  it  in  water  for  four  or  five  minutes,  so 
as  to  prevent  it  from  breaking.  One  such  treatment  of  the  borax  is 
all  that  is  necessary.    The  milky  liquid  you  have  produced,  as  described, 


78  OPTICAL    SHOP    PRACTICE 

should  be  applied  to  the  parts  that  are  to  be  soldered,  using  for  the 
purpose  a  small  camel  hair  brush,  or  the  frayed  end  of  a  toothpick 
will  do. 

Two  common  water  glasses,  one  containing  water  and  the  other 
one  part  of  sulphuric  acid  to  nine  parts  of  water  will  be  needed. 
Nearly  all  metals  have  a  tendency  to  oxidize,  or  blacken,  when  they 
are  heated  sufficiently  for  the  solder  to  flow  freely,  but  if  after  the 
soldering  is  done  the  frame  or  mounting  is  dipped  into  the  sulphuric 
acid  solution  the  dirt  and  borax  will  be  removed  by  the  liquid  and  the 
parts  will  be  left  clean. 

x\s  to  the  solder,  there  are  many  brands  of  gold  and  silver  hard 
solder,  about  the  best  of  which  is  what  is  termed  ''easy  flowing  solder," 
which  can  be  obtained  at  any  optical  wholesale  house.  It  usually 
comes  in  strips,  so  that  it  can  be  cut  up  as  needed.  Small  pieces  about 
two  millimeters  square  are  generally  used,  as  it  is  just  as  well  to  cut 
the  solder  up  in  this  way. 

It  will  be  a  very  good  idea  to  get  some  old  temples  and  some  old 
eye  wire  and  do  a  lot  of  practice  work  on  these  before  attempting  to 
do  any  regular  work.  No  matter  in  what  line  of  work  it  is  involved, 
successful  soldering  is  a  knack,  and  this  is  especially  so  in  optical' 
work. 

It  is  highly  important  to  know  how  to  regulate  the  gas  flow  and 
get  the  right  pressure.  It  is  best  to  fasten  the  blowpipe  on  the  bench 
so  that  the  hands  may  be  free  to  hold  the  work,  and  a  rubber  tube 
fastened  to  the  blowpipe  enables  you  to  move  your  head  if  necessary 
in  watching  the  work,  while  you  furnish  the  pressure  with  your  mouth 
for  the  blowpipe. 

Here  is  where  you  will  need  tools.  They  are  not  many,  neither 
do  they  involve  the  expenditure  of  much  money,  and  once  you  have 
them  you  will  probably  not  need  to  replace  most  of  them  for  years 
unless  through  losing  or  breaking  some.  Get  two  or  three  pairs  of 
pliers,  also  two  or  three  pairs  of  tweezers  of  different  sizes.    A  very 


SOLDERING    AND    REPAIRING  79 

handy  adjunct  to  your  set  are  a  small  airvil  and  vise,  especially  when 
riveting,  removing  screws,  etc.  Get  a  good  selection  of  screwdrivers 
with  different  blade  sizes,  some  with  swivel  tops,  others  with  wooden 
handles.  You  will  frequently  find  that  screws  have  rusted,  and  these 
are  easily  removed  by  the  use  of  a  tool  known  as  a  ''screw  extractor," 
which  can  be  bought  at  any  optical  house.  Also  have  a  small  hammer, 
for  riveting  work.  A  good  assortment  of  files  is  necessary.  Get  two 
or  three  fiats,  two  or  three  half-round  and  one  or  two  files  for  slotting 
screw  heads — about  No.  4  cut  is  the  best  for  the  majority  of  jobs. 
It  is  best  to  have  an  assortment  of  wooden  handles  for  the  files. 

Some  gold  repair  men  keep  an  assortment  of  rouge  and  emery 
sticks,  but  these  are  not  used  to  any  great  extent.  One  thing  is  abso- 
lutely necessary,  and  that  is  a  buff  head,  or  polishing  head,  to  insure 
good  work  and  keep  your  accessories  bright  and  attractive.  While 
you  can  obtain  these  at  various  places,  it  is  best  to  go  to  an  optical 
house,  for  there  you  will  get  exactly  what  the  optical  worker  uses. 
With  the  buff  head  you  will  need  a  brush  wheel,  a  felt  wheel  and  a 
cotton  buff,  all  of  which  should  be  about  three  or  four  inches  in 
diameter.  The  buff  head  should  run  about  2,500  revolutions  per 
minute. 

To  clean  up  any  part  that  has  been  filed,  emery  paste  should  be 
used.  The  cotton  or  felt  wheel  buff  is  used  to  put  the  last  finish  on  the 
work,  and  great  care  should  be  taken  when  using  this  wheel,  as  it  has  a 
tendency  to  "pull,"  and  it  will  easily  catch  the  frame  or  mounting  and 
bend  it  out  of  shape  or  break  it  into  small  pieces.  Both  emery  paste 
and  polishing  rouge  can  be  purchased  at  any  optical  house. 

In  addition  to  the  above  articles  it  would  be  a  good  idea  to  get 
a  good  jeweler's  brush,  a  spool  of  binding  wire  and  three  or  four 
solder  burrs.  You  will  very  likely  add  other  tools  as  you  go  along 
with  your  work,  but  those  already  named  are  the  essentials,  and  with 
plenty  of  practice  with  them  you  will  be  in  shape  to  do  the  small  amount 
of  repair  work  that  may  be  required  of  you. 

As  a  beginner  you  should  not  attempt  to  do  any  hard,  difficult 


80 


OPTICAL    SHOP    PRACTICE 


jobs.  The  thing  to  do  is  to'  turn  them  over  to  the  wholesale  houses, 
which  employ  thoroughly  experienced  workers  and  you  will  find  it 
cheapest  in  the  long  run. 


Doing  the  Work 

When  you  are  about  to  solder  a  frame  make  sure  that  the  parts 
are  perfectly  clean.  A  file  is  the  best  for  this  purpose.  Use  a  half 
round  file,  as  with  it  you  have  the  means  for  reaching  the  work  at 

any  angle,  and 
since  the  file  is 
pointed  you  can 
reach  into  the 
smallest  recesses. 
After  you  have  the 
work  perfect  ly 
cleaned  pin  or 
clamp  it  to  the 
soldering  block. 

Now,  with  the 
soldering  fluid  pre- 
pared in  the  de- 
pression in  the 
soldering  slate  as 
previously  instructed  take  your  camel  hair  brush  and  paint  the  parts 
to  be  soldered  with  the  soldering  fluid  and  then  also  apply  a  small  piece 
of  the  solder — about  2  millimeters  square — at  the  juncture.  You  are 
now  ready  for  the  heat,  and  a  small  flame  that  comes  to  a  point  like 
the  point  of  a  lead  pencil  and  about  two  or  three  inches  long  is  about 
the  right  kind  to  use. 

Approach  the  piece  of  solder  with  your  flame  about  three  or  four 
inches  away.  Now  you  will  notice  that  as  the  heat  strikes  the  solder 
and  borax  it  will  dry  the  latter,  having  a  tendency  to  make  it  curl, 
or  boil  up.    This  will  move  your  solder.     You  can  overcome  this  by 


SOLDERING    AND    REPAIRING  81 

a  piece  of  wire  in  your  left  hand,  with  which  you  can  hold  the  solder 
in  place.  Then  come  close  with  the  flame,  and  as  soon  as  the  solder 
begins  to  melt  leave  it  as  it  is  and  proceed  to  heat  the  wire  until  the 
solder  will  run  into  the  proper  place. 

There  are  several  gas  brackets  and  other  contrivances  made  for 
soldering  work.  Some  repair  men  use  an  air  pressure  pump,  others 
use  a  mouth  blowpipe.  Nearly  all  optical  jobbers  sell  these  soldering 
brackets,  and  the  latter  are  recommended  in  preference  to  others,  as 
they  are  made  especially  for  optical  work,  and  can  be  relied  upon. 

After  the  soldering  operation  has  been  completed  and  the  work 
is  still  hot  dip  the  entire  frame  into  the  sulphuric  acid  solution,  after 
which  rinse  it  in  clean,  plain  water.  This  will  remove  all  dark  spots 
and  leave  the  work  in  good  condition  for  polishing. 

It  is  not  an  easy  task  to  learn  to  make  the  solder  flow  properly, 
but  by  practice  and  exercising  good  judgment  this  can  be  accomplished. 
Watch  closely  and  determine  the  right  amount  of  heat,  also  the  correct 
amoimt  of  solder  to  use  on  a  given  job.  If  you  put  too  much  solder 
on  the  work  it  will  leave  a  lump  which  must  be  filed  down,  and  if 
this  is  necessary,  after  the  filing  put  the  work  on  the  brush  wheel, 
followed  by  the  cotton  buff.  Remember,  the  buff  should  always  be 
run  toward  you.  Keep  your  eye  on  the  work  all  the  time.  If  you 
don't  trouble  is  sure  to  result. 

If  you  are  given  a  spectacle  frame  to  repair  it  is  a  good  idea  to 
take  off  the  temples;  or  the  zylo  guards  if  the  job  is  an  eyeglass 
mounting.  Indeed  you  should  first  examine  a  job  carefully,  and  if  you 
feel  that  there  is  danger  of  spoiling  any  part  it  is  better  to  refuse  the 
work. 

You  can  purchase  at  any  optical  jobbing  house  whatever  bridges 
you  may  require,  all  ready  to  solder  onto  the  eye  wire;  you  can  also 
get  blank  bridge  stock,  which  you  can  bend  to  whatever  shape  you 
wish.  Before  doing  this  work  it  will  be  well  to  practice  bridge  bend- 
ing with  some  old  wire.     First  the  shank,  then  following  with  the 


82  OPTICAL    SHOP    PRACTICE 

right  curve  for  the  nose.  Be  careful  of  one  thing — you  will  often 
find  that  frames  and  mountings  brought  in  for  repairs  have  been 
soldered  previously,  and  when  this  is  the  case  and  you  think  that 
re-soldering  might  weaken  the  frame  or  mounting,  don't  take  any 
chances,  but  turn  the  job  down. 

It  will  never  pay  the  repair  man  to  try  to  make  springs,  handles, 
guards  or  other  small  parts  used  in  repairing.  As  for  steel  optical 
goods,  they  are  almost  a  thing  of  the  past  and  it  is  a  waste  of  time 
to  bother  with  them.  Zylo  frames  are  very  popular,  but  when  one 
of  these  is  broken  the  customer  should  be  advised  to  buy  a  new  one 
rather  than  to  attempt  repairs.  It  will  be  found  most  satisfactory  to 
all  concerned.    This  also  applies  to  zylo  temples. 

It  is  well  to  have  on  hand  a  bottle  of  assorted  screws,  also  several 
taps,  so  that  you  can  cut  a  thread  and  fit  a  new  screw  when  necessary. 
Do  not  try  to  repair  gold-filled  guards  or  springs,  for  they  cost  so 
little  that  it  is  better  to  get  new  ones;  the  same  way  with  zylo  pads, 
cork  pads,  shark-skin  pads,  etc.  You  had  better  have  repairs  on 
lorgnettes  and  folding  oxfords  done  at  the  wholesale  houses,  where  the 
workers  are  familiar  with  the  same. 


Quiz 

1 — Why  do  you  use  a  blowpipe?    Describe  how  you  use  it. 

2 — What  is  a  soldering  block?     From  what  made?    What  is  the  soldering 
solution  and  how  made  and  applied? 

3 — Name  the  tools  usually  needed    in  connection  with  soldering. 

4 — How  do  you  prepare  the  work  for  soldering?    Describe  the  process  of 
soldering. 

5 — How  does  gold  look  just  after  being  soldered?  How  do  you  remove  thii 
appearance  ? 

6 — What  is  the  buffer  head?    Why  used?    What  kind  of  wheels  are  used  on 
the  polishing  head?     At  what  speed  should  latter  be  run? 

7 — What  should  you  use  on  the  brush  wheel  ?    What  on  the  cotton  buff  ? 


\0W  that  you  have  fin' 
ished  this  little  vol- 
ume and,  we  trust, 
have  profited  by  its  mes- 
sage, by  building  a  firm 
foundation  for  your  future 
success,  its  dedication  to 
the  practical  shopman  be- 
ing accompanied  by  the 
Very  best  wishes  for  your- 
self and  fellow  workers,  we 
would  add  just  one  last 
word: 

In  all  your  'practice,  in 
the  shop,  in  the  office,  at 
all  times  have  as  your 
companion  and  guide 


WEEBCLY 

CHICAGO 


Page 

Bifocals    33 

Cementing 33 

Centering , 35 

Chipping   16 

Cutting 9 

Drilling  and  Mounting 27 

Edging   19 

Beveled  Lenses  20 

Rimless  Lenses  21 

Fitting   24 

Metal  Frames   25 

Zylo  Rims 24 

Lens  Terms  and  Their  Meaning 32 

Optical  Lenses   31 

Soldering  and  Repairing 77 

Surfacing  39 

Bifocal  Lenses    56 

Blocking    40 

Kryptoks    59 

Machinery 41 

Meniscus   Lenses    53 

Polishing  47 

Rough  Cylinders 49 

Roughing 44 

Toric  Compounds 54 

Toric  Kryptoks    67 

Ultex,  Onepiece  Bifocal  Lenses 73 

Transposition 68 


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OPTO 

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This  insures  having 
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Avoids  unnecessary 
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minimum  cost. 

A  place  for  every- 
thing. Made  section- 
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Large  Capacity.      Low  Price.      Send  for  Opto  Booklet 


Geo,  S.  Johnston  Company 

MANUFACTURING    a^^  WHOLESALE  OPTICIANS 

LOS  ANGELES  CHICAGO  NASHVILLE 

NEW  ORLEANS  PEORTA  EVANSVILLE 

DAVENPORT 


14  D/ Y  U^^ 


Optical  Shop  Equipment 


BUSINESS  GROWTH  FOLLOWS  A  SAT(SFy(NG  SERVICE  WHICH 
CANNOT  BE  SECURED  WITHOUT  ADEQUATE  SHOP  EQUIPMENT 


THE  ROBINSON  OPTICAL  COMPANY  SPECIALIZES  IN  THE 

MANUFACTURE  OF  HIGH  GRADE  SHOP  OUTFITS  USED  IN 

THE  PRODUCTION  OF  SPECTACLE  LENSES 

Our  line  includes  surfacing  and  edging  machinery, 
opticians  benches,  adjustable  tables,  grinding  (aps, 
curv/e  gauges,  lens  blocks,  tools,  shop  supplies,  etc. 

Our  catalog  illusfrafes  and  describes  such  equi'pmenf  and  contains 

inferesfiog  conf)Puting  charts  for  dcterminrng  the  geonf)etrlcal 

properties  of  lenses.  A  copv'  will  be  sent  on  request. 


THE  ROBINSON  OPTICAL  COMPANV 

Manufacturers  of  Optical  Equipment 
COLUMBUS  OHIO 


\Ti7-T^  T   T    o-m  coas^4D7'?a 

WELLSWuK.  1  n 


y. 


Automatic  Edging  Machine 
M  84 


Patented 


The  optical  shop  fitted  with  Wellsworth  Machines  is  able  to  produce 
work  of  a  quality  unexcelled ,  and  with  economy.  There  is  a  reason  for 
this — Wellsworth  Machines  are  past  the  experimental  stage — every 
one  is  tried  and  true. 

There  is  a  recent  edition  of  the  Wellsworth  Machinery  Catalog  just  off 
the  press  waiting  to  be  sent  to  you.     Shall  we  send  it? 

American  Optical  Company 

Southbridge,  Mass.,  U.  S.  A. 


